Abstract: A field experiment using hybrid Zhengdan 958 was conducted to study the effect of different fertilization methods on activities of several key enzymes in carbohydrate metabolism and grain yield of summer maize. The fertilization methods used in the study were fertilizing in seed furrow (T1), fertilizing in seed furrow + topdressing nitrogen at small bugle stage (T2), fertilizing in seed furrow + topdressing nitrogen at jointing stage + topdressing nitrogen at big bugle stage (T3) and using controlled-release fertilizer (T4). The results showed that T3 not only increased shoot dry weight, leaf area index (LAI) and activity of sucrose phosphate synthase (SPS) in leaves, but also enhanced activities of sucrose synthase (SS) and acid invertase (AI) in seeds, indicating that T3 treatment could enhance both carbohydrate supply ability of leaves and conversion ability of seeds. Therefore, yield parameters were improved and higher grain number per ear and grain yield per unit area were obtained by the fertilization method of T3 treatment.