Effect of different soil amendment of polyacrylate(potassium polyacrylate,polyacrylamide,potassium humate,potassium polyacrylate+potassium humate,polyacrylamide+potassium humate)on soil microbial biomass nitrogen and soil enzyme activity was studied in oat field.The results showed that different soil amendments all could increase the content of soil organic matter,available N,available P and available K,and each index increased by 824%~3022%,760%~1929%,515%~2945% and 2786%~6886% compared with contrast.Soil amendment significnatly increased soil microbial biomass nitrogen of 0~10,10~20 and 20~40 cm soil layer in the growing stages of oat.Soil microbial biomass nitrogen of potassium polyacrylate+potassium humate and polyacrylamide+potassium humate were higher than that of the single use,and with the increase of soil depth,soil microbial biomass nitrogen decreased.Compared with CK,Soil amendment significnatly increased soil determine catalase of each soil layer in the growing stages of oat，the activity was the highest at the heading stage,and potassium polyacrylate+potassium humate was the highest.Howerve,the urease activity of potassium humate,potassium polyacrylate+potassium humate and polyacrylamide+potassium humate treatments was lower than that of CK at the seeding stage,and higher than CK at the heading and maturity.The two enzyme activities decreased with the increase of soil depth.