Abstract: In order to analyze the effect of amino acid fertilizer on the growth, development and yield of soybean, and to explore the frequency and period of high-efficiency fertilization of amino acid fertilizer in soybean fields, two soybean varieties, Shennong 8（determinate type） and Shennong 9（semi-determinate type）, were used as materials.We set up fertilizer treatments, sprayed different times of amino acid fertilizers in different growth periods, to analyze the photosynthetic physiology, nitrogen metabolism, plant agronomic traits and yield of soybean leaves of different treatments at different growth periods.The results showed that the amino acid fertilizer treatment could significantly increase the yield of soybean. The yields of Shennong 8 and Shennong 9 were significantly higher than those of the other treatments when the amino acid fertilizer was sprayed three times in the V4, R1 and R3 periods, increased by 27% and 16% respectively compared with the control without amino acid fertilizer. The net photosynthetic physiological index, population light energy interception rate, nitrogen metabolism enzyme activity and nitrogen accumulation of the two varieties were significantly higher than other treatments in V4, R1 and R3 stages after three times spraying of amino acid fertilizer. The results showed that the application of amino acid fertilizer could improve the photosynthetic capacity and nitrogen metabolism of soybean plants, increase the seeds number per plant, and thus obtain high yield, and the highest yield was obtained by spraying three times of amino acid fertilizer at V4, R1 and R3 stages.