In order to study the comprehensive dynamic effects of different straw biochars on the soil acidity, nutrients and oil and Cyperus esculentus growth and yield of farmland in Hainan. The experiment set up six treatments:blank（CK）, rice straw biochar（RN1）, corn straw biochar（RN2）, wheat straw biochar（RN3）, Cyperus esculentus straw biochar（RN4）, bamboo charcoal（RN5）. Biochar was applied at a concentration of 5%, the physical and chemical properties of soil, enzyme activity, microbial community abundance, growth index and yield of oil Cyperus esculentus were measured before and after application. The results show that adding appropriate amount of biochar can significantly increase soil pH, organic matter content, ammonium nitrogen content, nitrate nitrogen content, available potassium content, available phosphorus content, significantly reduce soil electrical conductivity, change soil microbial community abundance, and significantly increase Cyperus esculentus. The number and yield of stalk tillers, of which rice straw biochar and Cyperus esculentus stalk straw biochar have significant effects in improving soil and increasing Cyperus esculentus stalk yield. In short, the addition of biochar can effectively alleviate soil acidification,regulate soil nutrient circulation, and promote the increase of yield and income of Cyperus esculentus and other crops.