To improve rapeseed yield, Brassica napus hybrid cultivar Huayouza 9 was selected as material, and was planted in pots and fields. Experiments were conducted to investigate the effects of wood vinegar application on seedling growth and seed yield under different foliar spraying times, different application intervals and different growth periods under 3 sowing dates. Results of pot experiments showed that total dry weight of rapeseed was significantly increased by 29.63%-74.07% when wood vinegar was sprayed for 2 to 4 times continuously and at intervals. At the same time, continuous and interval spraying of wood vinegar for 4 times could significantly increase leaf area by 81.58%-85.65%. Results of field experiments showed that the final seed yield treated by spraying once, twice and three times at seedling stage, bud bolting stage and flowering stage respectively increased by 3.30%, 9.52% and 11.38%, and protein content decreased by 2.62%, 4.02% and 4.68%, respectively. Compared with control, field yields of 3 different sowing dates sprayed with wood vinegar were increased by 20.13%, 23.25%, 13.97%, and the number of effective pods per plant increased by 47.29%, 61.87%, 72.90%, respectively. Comprehensive analysis showed that the promotion effect was better when wood vinegar was sprayed 2 to 4 times during growth period, with an interval of more than 5 days each time. Under different sowing dates, the effect of wood vinegar on rapeseed growth and yield was more significant in the suitable sowing date (on Oct. 9th). [ABSTRACT FROM AUTHOR]