In order to make good use of the straw resources and reduce the application levels of nitrogen fertilizer, a two-factor design of nitrogen fertilizer application(conventional nitrogen application(N1), reduction 20% of nitrogen fertilizer(N2)) and the application of different straw decomposing inoculants(without the application of straw decomposing inoculant(T0), “Dahua” straw decomposing inoculant(T1), “Ningliang” straw decomposing inoculant(T2), and “Jiuye” decomposing inoculant(T3)) were performed to investigate the effects on the growth, yield and quality of summer corn(Zhengdan 958) under the condition that all preceding crop(rape) straw was returned to the field. The results showed that the application of straw decomposing inoculant and nitrogen fertilizer reduction could shorten the growth period of summer corn by 1-4 days. The leaf area index(LAI) was higher in treatments with straw decomposing inoculant than that of without straw decomposing inoculant, and excessive application of nitrogen fertilizer decreased the LAI. The application of straw decomposing inoculant made the dry matter accumulation of summer corn under N1T2 treatment reach 14 342.89 kg/hm2 in the ripening period. The highest grain yield was obtained under N2T3 treatment, 10.88% higher than that of N1T0 treatment. Applying straw decomposing inoculant could increase the content of the protein and free amino acid of summer corn. Nitrogen fertilizer reduction could increase the soluble sugar content of summer corn grain, but the content of free amino acid was reduced.