Abstract: Based on the flowering observation experiment of rapeseed （Brassica napus L.） in Huaihua agricultural meteorological experiment station from 2011 to 2020, the effective pod number and single pod grain number of rapeseed flowering in different types of weather were obtained, and the cold accumulation temperature index was used to comprehensively express the low temperature intensity and low temperature duration. Through correlation analysis, stepwise regression statistics and other methods, the relationship model between effective pod rate, single pod grain number and cold accumulated temperature of rape was established, and the index of damaged cold accumulated temperature during flowering was studied. The results showed that low temperature and rain lasting for 3~5 days or simple short-term low temperature （including individual frost days and daily minimum temperature of about -0.5 ℃） had little effect on seed setting of rape. The effective pod rate was 80%~99% of that in normal weather, and the number of single pod seeds was（20.1±1.6）, which was equivalent to 91% of that in normal weather. The effective pod rate was 20%~77% （average 61%） and the number of single pod seeds was 27%~56% （average 47%） of that in normal weather when low temperature and rain lasted for more than 7 days or frost accumulated for more than 3 days or frost accumulated for more than 40 hours. When the flowering period lasted for 4 days, the key period of cold accumulation temperature was from 2 days before flowering to 3 days after flowering. When the effective pod rate or single pod grain number reached 70% of that in normal weather, the cold accumulation temperature indexes in low temperature weather were ≥ 36.0 ℃ and ≥ 29.7 ℃, respectively, and the cold accumulation temperature indexes in low temperature and rainy weather without sunshine were ≥ 21.2 ℃ and ≥14.3 ℃, respectively.

Key words: rapeseed（Brassica napus L.）, effective pod rate, number of seeds per pod, cold accumulated temperature, simulation