In order to elucidate the effects of organic fertilizer amendment on soil nitrogen transformation and the amounts of different form of soil N,a three-year location trail was fulfilled in calcareous soil under dip irrigated cotton field,soil mineral N concentration(NH+4,NO-3),soil microbial N biomass as well as soil total N content were determined.The treatments contain CK,CF(N 300 kg·hm-2,P2O5 90 kg·hm-2,K2O 60 kg·hm-2) and different types(cattle manure and Bio-organic fertilizer ) and levels(3 000 kg·hm-2 and 6 000 kg·hm-2) of organic material combined with 60%(N 180 kg·hm-2,P2O5 54 kg·hm-2,K2O 36 kg·hm-2) or 80%(N 240 kg·hm-2,P2O5 72 kg·hm-2,K2O 48 kg·hm-2) NPK chemical fertilizer.There was a significant influence of organic fertilizer amendment on improving soil NH+4-N and NO-3-N concentration(P＜005) as well as increasing the ratio of soil NH+4 to soil total N.The highest soil mineral N was obtained in 60% CF+BF2 treatment.Soil total N and soil microbial N were significantly increased after the continuous 3-year organic fertilizer application.Compared with CK and CF,soil TN content increased by 24.7%～37.1% and 13.3%～24.5%,meanwhile,soil MBN increased by 53.8%～98.5% and 32.2%～70.5% respectively,with different treatments of organic fertilize supply.Moreover,bio organic fertilizer treatment(CF+BF) had an obvious role on enhancing the proportion of MBN/TN,and organic fertilizer combined with chemical fertilizer improved soil nitrification potential and soil mineralization capacity.In conclusion,there was an significant effect of 3 000～6 000 kg·hm-2 organic fertilizer application on promoting soil nitrogen transformation,improving soil N fertility and optimizing the ratio of different forms of soil N under drip irrigated cotton field.