Abstract: Outcrossing rate in an open-pollinated breeding population(Huli population,Chaling,Hunan Province) of Caldesia parnassifolia was estimated by the dominant RAPD makers using 10 open-pollinated progeny arrays of 24 individuals.The multilocus outcrossing rate(t_m) was 1.008 and the single-locus outcrossing rate(t_s) was 1.028.The multilocus outcrossing rate did not significantly differ from the single-locus outcrossing rate(t_m-t_s =-0.021).The fixation index(F) was-0.200.The estimates of (t_m),(t_s) and F utilizing windows version of MLTR program clearly indicate that outcrossing is predominant in the C.parnassifolia open-pollinated breeding population.This is possibly influenced by factors such as plant density,the adaptability of pollinator and so on.