One of the important ways to improve the properties and application effect is to add microbial community with biological activity into organic cultivation substrate.In this experiment,the effects of arbuscular mycorrhizal fungi (AMF) on seedling growth,fruit yield,photosynthesis,microbial diversity and enzyme activities in rhizosphere of Capsicum annuum L.plants were investigated by adding AMF in organic substrate during seedling and cultivation.The results showed that:(1)The growth of pepper seedlings was promoted.(2)The net photosynthetic rate(Pⁿ),stomatal conductance(G^s),transpiration rate(T^r) and water use efficiency(WUE) were significantly increased while intercellular CO² concentration(Cⁱ) was decreased.Meanwhile,it has little effect on the maximum photochemical efficiency(F^v/F^m),but the actual photochemical efficiency(Ф^PSⅡ),photochemical quenching(q^P) and table electron transport efficiency(ETR) were increased by AMF,moreover,resulting in robust seedlings and higher yield.(3)The amount of bacteria and actinomycetes in rhizosphere of pepper plants was increased by AMF,but the amount of fungi was decreased,and the Shannon-Wiener and Shannon index of microbial diversity,the activities of catalase,urease and alkaline phosphatase in organic substrate were enhanced.Furthermore,the correlation coefficient between amount of bacteria,actinomycetes,fungi and activities of enzymes such as catalase,urease and alkaline phosphatase in AMF substrate reached to a significant or extremely significant level.Our results suggested that AMF increased stomatal conductance of Pepper leaves and improved electron transfer rate,raised CO² assimilation efficiency and net photosynthetic rate;meanwhile it also promoted the transformation process of substrate from low-fertility caused by fungi to high-fertility caused by bacteria,and enhanced microbial diversity and enzyme activities.AMF helps maintain the stability and harmony in rhizosphere ecological system of pepper plants,lead to more rapid seedlings growth and higher yield.In conclusion,it is an effective way to improve the application effect of organic substrate by adding AMF.