Abstract: High-starch content, wax and sweet maize were used to study the effect of nitrogen utilization on the sucrose synthesizing in spike leaf. The result indicated sucrose content and photosynthesis rate decreased gradually after 7 days behind tassel. The difference of nitrogen treatment was significance and the response of varieties to nitrogen was different. SPS activity changed as the same as photosynthesis rate. SS activity changed as single apex after tassel. The date of appearance of apex was 28 days after tassel and decreased rapidly after 35 day. SS activity was different among varieties.