Abstract: In order to explore the effects of sowing date on growth process, agronomic traits and yield formation of soybeans in the third cumulative temperature zone, and further optimize the sowing date of soybeans, soybean varieties Dongsheng 17, Dongsheng 23 and Heihe 43, which have an extensive planting area in Heilongjiang Province were adopted in Hailun City from 2020 to 2022. The effects of four sowing dates (May 9, 16, 23 and 30) on growth period and yield were examined. The results showed that with the delay of sowing date, the growth process of soybean was delayed, and the vegetative growth period, reproductive growth period and whole growth period of soybean were shortened with the most significant shortening of vegetative growth period (P < 0.05). In the four sowing dates, pod number per plant, kernel number per plant, 100 kernel weight and yield of the three soybean varieties were higher in the early sowing dates but lower in the late sowing dates with the kernel number per plant affected the most significantly. The highest yield obtained for the three varieties in the sowing date experiment for Dongsheng 17, Dongsheng 23 and Heihe 43 was 3 871, 3 322, 3 484 kg·hm⁻² in 2020, 4 187, 2 627, 3 636 kg·hm⁻² in 2021, 3 532, 2 804, 3 373 kg·hm⁻² in 2022, respectively. Significant yield differences were observed among sowing dates (P < 0.05). The influence of meteorological factors on soybean yield by multiple regression analysis model showed that the proportion of influence on yield change was in the order of accumulated temperature in reproductive growth period, precipitation in vegetative growth period, precipitation in reproductive growth period and accumulated temperature in vegetative growth period. Soybean varieties Dongsheng 17, Dongsheng 23 and Heihe 43 could obtain the highest yield when sown in the middle of May.