Abstract: In order to ensure the high yield of the mode of rapeseed-early season rice-late season rice and overcome season contradiction of the rapeseed-early season rice-late season rice cropping system in Jiangxi Province .To explore the growth and yield affected by different symbiosis period, the experiment was carried out in double cropping rice area of Jiangxi, Setting symbiosis period of rapeseed-rice were 10 d (D10), 5 d (D5), 0 d (D0, CK). The results showed that:(1) the D5, D10 treatments were basically identical with the maturity period of CK , but increased 5-7 days from the seedling stage to the budding stage, and extended the nutrition growth period of rapeseed, which was effective for nutrient accumulation at former stage, eventually laid the ground for achieving high yield. (2)The rapeseed undersowing rice was favorable for improving the density at the seedling stage, but the density at the other growth stages decreased with extension of symbiosis period, resulting in the seedling rate and plant rate of rapeseed decreased with extension of symbiosis period, the density of D5 treatment was biggest, followed by CK treatment, D10 treatment has the least density, 42.35×104ha-1, 40.02×104ha-1 and 36.68×104ha-1 respectively. (3)The symbiosis time influenced the growth and development at each period, it was favorable for ontogeny and yield per plant when symbiosis time delayed, but the yield of D5 treatment was highest, followed by D10 treatment, CK treatment has the lowest yield, 1564.12 kg/hm2, 1430.72 kg/hm2, 1402.37 kg/hm2, respectively. According to the results, suggest a favorable condition of 5 to 10 days symbiosis period of rapeseed-rice for getting higher yield undersowing rice of the mode of rapeseed-early season rice-late season rice, 5 days was best, should sow in suitable symbiosis as early as possible.