A two-year field experiment was conducted to illustrate the effects of sowing date on cottonseed properties at different fruiting-branch positions(FBPs).Two cotton cultivars(Kemian 1 and Sumian 15)were sowed on 25 April,25 May,and10 June in 2010 and 2011,respectively.The boll maturation period increased with the delaying of sowing date.Normal sowing treatment(25 April)had higher seed weight,embryo weight,embryo oil content and protein content than late sowing treatments(25 May and 10 June).The flowering date,seed weight,embryo weight,embryo oil and protein contents,and the dynamic changes of embryo oil and protein contents were altered by different FBPs.A significant interaction of sowing date×FBP was observed on embryo weight,embryo oil content,embryo protein content and the dynamic changes of embryo oil and protein contents,but was not observed on seed weight.Seed weight,embryo weight,embryo oil and protein content had significant positive correlations with the mean daily temperature(MDT),mean daily maximum temperature(MDTmax),mean daily minimum temperature(MDTmin),and mean daily solar radiation(MDSR),indicating that temperature and light resources were the main reasons for different sowing dates affecting the cottonseed properties at different FBPs.Moreover,the difference in MDT was the main difference in climatic factors among different sowing dates. A two-year field experiment was conducted to illustrate the effects of sowing date on cottonseed properties at different fruiting-branch positions (FBPs). Two womans cultivars (Kemian 1 and Sumian 15) were sowed on 25 April, 25 May, and10 June in 2010 and 2011, respectively. The boll maturation period increased with the delaying of sowing date. Normal sowing treatment (25 April) had higher seed weight, embryo weight, embryo oil content and protein content than late sowing treatments (25 May and 10 June) The flowering date, seed weight, embryo weight, embryo oil and protein contents, and the dynamic changes of embryo oil and protein contents were altered by different FBPs. A significant interaction of sowing date × FBP was observed on embryo weight, embryo oil content , embryo protein content and the dynamic changes of embryo oil and protein contents, but was not observed on seed weight. Seed weight, embryo weight, embryo oil and protein content had significant positive correlations with the mean daily temperatur mean daily maximum temperature (MDTmax), mean daily minimum temperature (MDTmin), and mean daily solar radiation (MDSR), indicating that temperature and light resources were the main reasons for different sowing dates affecting the cottonseed properties at different FBPs.Moreover, the difference in MDT was the main difference in climatic factors among different sowing dates.