Abstract: In order to explore the effects of different levels of lactic acid bacteria combination on nutrient composition, fermentation quality and aerobic stability of defective pear fermentation, the experiment used defective pear as raw material, Lactobacillus plantarum and Bacillus subtilis were mixed at a ratio of 1∶1 and were added to the crushed defective pear at different levels（0, 1.14×10~4, 1.29×10~5, 1.38×10~6, 1.45×10~7, 1.58×10~8 cfu/g） for fermentation. The treatments were named CK, La, Lb, Lc, Ld and Le, respectively. After 30 days of fermentation, the sensory quality, nutrient composition, fermentation quality, pH value and microbial number of defective pear fermentation were determined. The results showed that the sensory score of CK treatment was 5, and the grade was medium. The sensory score of La treatment was 13, and the grade was fair. The sensory score of Lb treatment was 19, and the grade was excellent. The sensory scores of Lc, Ld and Le were all 20, and the grades were excellent. With the increase of lactic acid bacteria combination supplemental level, the crude protein and soluble carbohydrate contents of defective pear fermentation showed an increasing trend generally, and the neutral detergent fiber content showed a gradually decreasing trend. The crude protein content and soluble carbohydrate content in CK treatment were significantly lower than those in other treatments（P＜0.05）, and the neutral detergent fiber content in CK treatment was significantly higher than that in other treatments（P＜0.05）. The crude protein content of Ld and Le treatments was significantly higher than that of La and Lb treatments（P＜0.05）, and had no significant difference with Lc treatments（P＞0.05）. The soluble carbohydrate content of Lb, Lc, Ld and Le treatments was significantly higher than that of La treatment（P＜0.05）. The content of neutral detergent fiber in Lc, Ld and Le treatments was significantly lower than that in La and Lb treatments（P＜0.05）. With the increase of lactic acid bacteria combination supplemental level, the pH value, ammonia nitrogen and butyric acid contents of defective pear fermentation showed a decreasing trend generally, the lactic acid and acetic acid contents showed a gradual increasing trend, and the ethanol content showed a decreasing and then increasing trend. The contents of pH value, ammonia nitrogen, butyric acid and ethyle alcohol and in CK treatment were significantly higher than those in other treatments（P＜0.05）, while the contents of lactic acid and acetic acid were lower than those in other treatments（P＜0.05）. The contents of ammonia nitrogen in Lc, Ld and Le treatments were significantly lower than those in La and Lb treatments（P＜0.05）. The acetic acid content in Lc, Ld and Le treatments was significantly higher than that in La and Lb treatments（P＜0.05）, the butyric acid content in La treatment was significantly higher than that in Lb, Lc, Ld and Le treatments（P＜0.05）, and the ethanol content in Ld treatment was significantly lower than that in CK, La, Lb, Lc and Le treatments（P＜0.05）. The propanol content in Lc and Ld treatments was significantly higher than that in La, Lb and Le treatments（P＜0.05）. With the extension of aerobic exposure time, the pH value, the number of yeast and mold of defective pear fermentation increased gradually, and the number of lactic acid bacteria decreased gradually. The pH value of Lb, Lc, Ld and Le treatments increased slowly, and was significantly lower than that of CK and La treatments under the same aerobic exposure time（P＜0.05）. The number of lactic acid bacteria in CK treatment decreased the fastest, while the number of lactic acid bacteria in other treatments decreased slowly. Under the same aerobic exposure time, the number of lactic acid bacteria in CK treatment was significantly lower than that in other treatments（P＜0.05）, and the number of lactic acid bacteria in Lc, Ld and Le treatments was significantly higher than that of La and Lb treatment（P＜0.05）. The quantity of yeast and mold in CK, La and Lb treatments increased rapidly. The number of yeast and mold in Lc, Ld and Le treatments increased slowly. Under the same aerobic exposure time, the number of yeast and mold in CK treatment was significantly higher than that in other treatments（P＜0.05）, and the number of yeast in Lc, Ld and Le treatments was significantly lower than that in CK, La and Lb treatments（P＜0.05）. These results indicated that the combination of Lactobacillus plantarum and Bacillus subtilis could improve the nutrient composition, fermentation quality and aerobic stability of defective pear fermentation, and on the whole, the effect was better when the supplemental level was 1.38×10~6 to 1.58×10~8 cfu/g.