Aiming to the Hetao irrigation area’ s current situation of long-term excessive application of chemical fertilizer and less application of organic fertilizer,this paper discussed the effect of replacing chemical fertilizer nitrogen with organic fertilizer nitrogen on the growth and development,nitrogen efficiency and yield of spring maize,which provided the theoretical basis for exploring the feasibility of combining chemimal fertilizer nitrogen reduction and organic fertilizer nitrogen application in Hetao irrigation area and the proportion of fertilizer reduction.The effect of replacing chemical fertilizer nitrogen with organic fertilizer nitrogen on the growth and development,nitrogen efficiency and yield of maize in Hetao irrigation area of Inner Mongolia was discussed by using field experiments,and by setting up five fertilization models of no nitrogen fertilization(CK),farmers’ conventional fertilization(CF),reduced fertilization(TS),replacing 30% fertilizer nitrogen with organic fertilizer nitrogen on the basis of TS(MF),and replacing 50% fertilizer nitrogen with organic fertilizer nitrogen on the basis of TS(OF).The result revealed that the nitrogen fertilizer application could speed up the maize growth,and the method of replacing fertilizer nitrogen with organic fertilizer nitrogen(MF,OF) was more effective in promoting the growth of maize. In tasseling stage,the leaf area indexes of MF and OF treatments were the highest,which were 60.4%,11.1%,35.6%,and 60.1%,10.9%,35.3% higher than that of CK,CF and TS respectively.In mature period,the OF treatment’s dry matter accumulation was the highest,which was 2.6 times of CK,and was 45.1%,43.0% and 57.7% higher than that of CF,TS and MF treatments respectively.Under the condition of same N application,the nitrogen efficiency and yield of maize could be improved more by replacing chemical fertilizer nitrogen with organic fertilizer nitrogen than only applying chemical fertilizer nitrogen(TS treatment). In terms of photosynthetic characteristics of maize,the effect of MF treatment was more obvious.The yields of MF and OF treatments were not significantly different from that of CF treatment.But the outputs of MF and OF treatments were 162.1% and 161.7% higher than that of CK treatment,32.6% and 32.4% higher than that of TS treatment respectively.The results of comprehensive analysis showed that the growth rate,leaf area index,photosynthetic characteristics,nitrogen efficiency and yield of maize could be significantly improved by replacing part of chemical fertilizer nitrogen with organic fertilizer nitrogen under the same amount of nitrogen application.Replacing 50% chemical fertilizer nitrogen with organic fertilizer nitrogen was a reasonable way of increasing the yield of spring maize and increasing the efficiency of nitrogen fertilizer in Hetao irrigation area of Inner Mongolia.