Abstract: Mikania micrantha is a worst weed that invaded South China.Three characters of seed production of M.micrantha populations were studied in this paper.The results showed that the mean flowers number,mean seed percentage,mean seed production and 1000-seed weight of these populations were various.The mean flower number ranged from 93281.6 to 154698.0 per 0.25 m²,mean seed percentage ranged from²5.75% to 34.58%,mean seed production ranged from²3673.40 to 52616.71 per 0.25 m²,mean 1000-seed weight ranged from 0.0880 to 0.1020 g .Seed settled in population mainly with sexual reproduction was bigger than that in population mainly with asexual reproduction.Combined adaptation of M.micrantha to environment,the results have been discussed.