Abstract: The effects of coal-based bio-organic fertilizer on potato yield, soil physical and chemical properties and abundance of nitrogen-cycling microbes under drip irrigation were studied, aiming to reveal the mechanism of the fertilizer on crop yield and soil nitrogen cycle. A field experiment was conducted from May to September in 2019, located in Guyang County, Inner Mongolia. Totally 1 500 kg/hm~2（BF1）, 3 000 kg/hm~2（BF2）, 4 500 kg/hm~2（BF3） of coal-based bio-organic fertilizer and no organic fertilizer（CF） were applied respectively on the same levels of chemical fertilizations. The chemical fertilizers were 210 kg/hm~2 of nitrogen（N）, 150 kg/hm~2 of phosphorus（P₂O₅） and 180 kg/hm~2 of potassium（K₂O）. The field experiment included four treatments and each treatment was repeated three times. Plant dry matter accumulation and tuber yield were quantified at potato maturity and harvest periods, respectively. Samples were collected from 0～20 cm layer for analysis of physicochemical properties of soil and abundances of nitrogen cycling microbes before tuber harvesting. The abundances of bacteria（16 S rRNA）, fungi（ITS） and nitrogen cycle functional genes（nirS, ammonia-oxidizing bacteria amoA, nifH） were quantified by quantitative real-time PCR techniques. Compared with CF, increasing the coal-based bio-organic fertilizer ratio could significantly increase the dry matter accumulation of plant and tuber. The total tuber yield was increased by 5.30%～9.49% with the organic fertilizer increasing. The soil pH value of organic fertilizer treatments was significantly lower but organic carbon content was higher than that of CF. The abundance of soil bacteria and fungi was decreased with the increase of organic fertilizer application, but it was higher than that of CF. The abundance of microbial genes related to soil nitrogen-cycling responded positively to the addition of organic fertilizer. Furthermore, the gene abundance of nitrite reductase（nirS） was significant, while nitrogenase（nifH） and ammonia monooxygenase（amoA） of ammonia-oxidizing bacteria（AOB） were not significant. The content of soil organic carbon appeared to be the key factor influencing the abundance of nirS-type denitrifying bacteria. Overall, these results indicated that the proportion of soil bacteria and fungi could be regulated through proper application of the coal-based bio-organic fertilizer. Soil nitrogen cycle would be affected by the coal-based bio-organic fertilizer. The abundance of nirS gene was more sensitive to the addition of organic fertilizer than that of other functional genes. The coal-based bio-organic fertilizer would help to improve the productivity of potato fields, and the application of 4 500 kg/hm~2 had a better performance.