Abstract: The purpose of this study was to investigate the changes of soil enzyme activity and microbial content after liquid amino acid organic fertilizer was substituted for partial chemical fertilizer. Six treatments of CK （no liquid organic fertilizer， 100% chemical fertilizer） were applied to two different varieties of hot pepper， T₁ （30% nitrogen fertilizer loss + amino acid liquid organic fertilizer）， T₂ （35% nitrogen fertilizer loss + amino acid liquid organic fertilizer）， T₃ （40% nitrogen fertilizer loss + amino acid liquid organic fertilizer）， T₄ （45% nitrogen fertilizer loss + amino acid liquid organic fertilizer） and T₅ （50% nitrogen fertilizer loss + amino acid liquid organic fertilizer）， the effects of nitrogen fertilizer with different gradient and amino acid liquid organic fertilizer on soil biological characteristics and nutrient content were studied， and the correlation was analyzed. After Amino acid liquid organic fertilizer replaced different proportion of chemical fertilizer， the urease activity， the Catalase activity and the dehydrogenase activity of both varieties of hot pepper increased， and the enzyme activity showed the trend of first increasing， then becoming flat or decreasing， the results showed that the enzyme activity was not proportional to the amount of organic manure， but increased the content of bacteria and actinomycetes and inhibited the content of fungi compared with CK， the value of soil pH increased in the treatment of amino acid liquid organic fertilizer， but the increase was not significant. It can provide theoretical support for organic manure to alleviate soil acidification， reduce EC value and further improve soil quality. It is considered that the substitution quantity of T₄ is the best.