Abstract: Mongolian pine（Pinus sylvestris var.mongolica） is an important timber,landscaping and afforestation tree species in North China.In order to provide theoretical basis for high quality,high yields and stable yields of cones and putting forward scientific management strategies,the effect of fruit-expander treatment on cones and nuts characters of P.sylvestris var.mongolica was studied.P.sylvestris planted in Qinhe seed orchards,Wangqing County,Yanbian,Jilin Province were used as materials to compare and analyze the effects of traits,including cone yield,cone quality,seed yield and seed quality,treated with two fruitexpanders including chlorinated urea andα-sodium-naphthyl acetate respectively.The average seed traits were higher than those of the control,indicating that fruit-expander treatment could promote the seed growth of P.sylvestris var.mongolica.The cone weight,cone yield,seed long and seed width of P.sylvestris var.mongolica were all significant in different variation sources（P＜0.001）,indicating that the fruit-expander treatment had a significant effect on the cone quality and yield.The phenotypic variation coefficient of cone yield and seed weight reached to 28.54%,33.88%,respectively.The cone traits were comprehensively evaluated for each treatment,and the optimal treatment was 10 mg·L^-1Chlorinated urea,and the real gains of cone length,cone width and cone weight were 11.81%,4.65%and 24.35%,respectively.The optimal treatment according to the seed traits was 10 mg·L^-1α-sodium-naphthynl acetate,and the real gains of seed yield per cone,seed weight,seed long,seed width,wing long and wing width were 21.32%,24.15%,0.24%,9.16%,0.33%and 2.16%,respectively.The results showed that chlorinated urea(10 mg·L^-1) andα-sodium-naphthyl(10 mg·L^-1)treatments could significantly improve the cone size and seed bearing of P.sylvestris var.mongolica.