Abstract: The aim is to study the optimal sowing date of different high-protein soybean varieties. 4 highprotein soybean varieties in Sanjiang Plain of Heilongjiang Province were used as materials, 7 different sowing dates were carried out in this study. The effects of the sowing date on seed quality and yield of high protein soybean were studied. The results showed that: the mean rang of protein content of the 4 high-protein soybean varieties was from 39.14% to 45.26%, and the maximum change was 15.64%. The mean range of fat content was from 18.82% to 20.30% , and the maximum change was 7.86% . The yield variation range was from 2064.2 kg/hm2 to 3068.1 kg/hm2. The mean protein yield range was from 807.2 to 1377.9 kg/hm2. Yield and protein yield increased first and then decreased with the sowing dates, and reached the maximum at A2 sowing date. The sowing date significantly affected the protein content, fat content, yield and protein yield of soybean. Therefore, the optimum sowing date can increase yield and protein yield of soybean, and the best sowing date in local climatic condition for high-protein soybean varieties is around May 4.