Abstract: Sex allocation theory assumes that there is a trade-off between male and female functions of relative investment,which depend on their fitness gain curves.One of factor accounting for sex allocation variation is size-dependent sex allocation.To test this prediction,we focused on Hedychium coccineum in Zingiberaceae that was extremely lack of research about sex allocation with size-dependency in present.In this study,we investigated reproductive traits of resource investment and allocation among field and transplanted populations in florescence and after flowering in 2009.Combined pollinator observation,regression models indicated that:① there was size-dependency within reproductive structure allocation in H.coccineum,but no consistent with SDS prediction in flowering period;② there were no variation with size-dependency in floral design size,attractive structure,sex allocation and male and female fitness gains,which might imply special adaptive significance.