Abstract: Based on a long-term fertilization split design experimentation, the effect of combined chemical fertilizer and straw application on photosynthetic property and yield of summer maize was determined. The main treatment in the study was chemical fertilization, and maize-straw fertilization was the sub-treatment. The variables investigated include leaf area, leaf area index and chlorophyll content. The results indicate that though long-term maize-straw application positively influences maize yield, a large-scale yield increase mainly relies on chemical fertilization. Yield for the combined application of maize-straw and chemical fertilizer is much higher than that for individual applications of the fertilizers. The indices for photosynthesis, leaf area, leaf area index increase with increasing application of chemical fertilizer, and the leaf area index keeps around 3.5 at the late filling stage. Long-term application of maize-straw increases leaf area and grain number hence yields. In comparison with chemical fertilizer, maize-straw application only or no fertilization decrease the chlorophyll content. The combination of maize-straw and chemical fertilizer further increases grain number and 1000-grain weight, delays leaf decrepitude and prolongs leaf functional period, eventually increases summer maize yield. Combined application of chemical fertilizer and crop straw is a better fertilization mode for high summer maize yield in the study area.