Abstract: In order to obtain the optimum sowing date of summer tartary buckwheat for high yield and better quality around Yunnan Kunming, three varieties (‘Yunqiao 1’, ‘Diku 1’ and ‘Jinku 6’) were selected to study the effects of four sowing date (June 25, July 5, July 15, July 25) on growth period, agronomic and yield traits. The results showed that, with the delaying of sowing date, the growth period of three tartary buckwheat varieties were all significantly shortened. The height, first branch number and stem node number had no systematic increase or decrease with the delaying of sowing date for all the three tartary buckwheat varieties. The number of seeds per plant, the thousand kernel weight, seed weight per plant and yield increased with the delaying of sowing date. Compared with early sowing (June 25), the yield of three varieties reduced by 69.4%-74.8% for sowing on July 5, reduced by 61.4%-93.3% for sowing on July 15 and reduced by 88.3%-94.7% for sowing on July 25. In this study, the suitable sowing date of summer tartary buckwheat for high yield and better quality in Yunnan was June 25, which could achieve the highest yield.