Abstract: In order to promote the growth of loquat seedlings and improve their photosynthetic capacity and resistance, ‘Dawuxing’ loquat seedlings were sprayed with different concentrations(0, 1, 2, 4 and 6 g·L^-1) of chitosan and different dilution times（0, 100,150 and 200 times） of microbial agents to study the effects of chitosan and microbial agents on photosynthesis and resistance physiology of loquat seedlings. The results showed that foliar application of different concentrations of chitosan increased chlorophyll content, peroxidase（POD） activity, superoxide dismutase（SOD） activity and catalase（CAT） activity of loquat seedlings. When the chitosan concentration was 2 g·L^-1, the content of chlorophyll a and chlorophyll b, carotenoid content, POD activity, SOD activity and CAT activity reached the highest value, increased by 28.03%, 25.66%, 6.84%, 49.25%, 15.72% and 83.75% respectively compared with the control. The treatments with different concentrations of microbial agents increased the contents of chlorophyll b, carotenoids and soluble protein in the leaves of loquat seedlings, and the content of chlorophyll a was increased only when the concentration was 100 times. The treatment with 50 and 100 times of microbial agents increased the activity of antioxidant enzymes. When the concentration was 150 times, only POD activity was increased. When the concentration was 200 times, there was no significant change compared with the control. Therefore, when the concentration of microbial agent was 100 times, the effect was the best. The content of chlorophyll a and chlorophyll b, carotenoid content, POD activity, SOD activity, CAT activity and soluble protein content in the leaves of loquat seedlings increased by 11.69%, 25.00%, 18.37%, 86.11%, 29.86%, 18.23% and 17.87%, respectively, compared with the control. Therefore, when the chitosan concentration was 2 g·L^-1 and the microbial agent concentration was 100 times, it was most conducive to improving the photosynthetic capacity and resistance of loquat seedlings.