Abstract: 【Objective】 The purpose of this project is to study the effect of previous crop on photosynthetic characteristics and yield of succeeding soybean crop.【Method】 There were 5 treatments 0(N₀), 225(N₁), 375 (N₂), 525 kg/hm² (N₃) of winter wheat, and no nitrogen application (CK) throughout the year. The effects of different nitrogen application rates on the chlorophyll content (SPAD), photosynthetic physiology and yield of post-wheat soybean leaves were studied.【Result】 The results showed that the different nitrogen application levels in the previous wheat season had an aftereffect on the photosynthetic characteristics and yield of the succeeding soybean crop. The summer soybean SPAD value, net photosynthetic rate (Pn), transpiration rate (Tr) and stomatal conductance (Gs) were the lowest, and the intercellular CO₂ (Ci) was the highest, which was significantly different from other treatments (P<0.05); with the increase of nitrogen application rate in the previous wheat season, the summer soybean SPAD value, net photosynthetic rate (Pn), transpiration rate (Tr) and stomatal conductance (Gs) increased continuously throughout the growth period. The trend of post-falling was the highest with N₂ treatment, while the intercellular CO₂ concentration (Ci) was the lowest, and the summer soybean yield was also the highest, reaching 3,164.64 kg/hm². Too low or too high nitrogen application in wheat season was not conducive to the increase of summer soybean yield. 【Conclusion】Under the conditions of this experiment, the nitrogen application rate of the previous wheat season was 375 kg/hm², and a certain amount of nitrogen fertilizer should be applied in the soybean season, and the photosynthetic capacity of the summer soybean leaves was the highest, so was the yield.