Field investigation was performed on the floral syndrome,pollination characteristics,pollinator behaviors and breeding system of Heteroplexis by continuous observations,TTC method,Benzidine-H₂O₂ method,out-crossing index,pollen-ovule ratio.The result as follows:(1)Under natural conditions,the flowering stage of Heteroplexis vernonioides was about 60 days from April to June,Heteroplexis microcephala and Heteroplexis incana were about 60 days from April to August,Heteroplexis impressinervia and Heteroplexis vernonioides were about 150 days from August to December.The life span of a single flower was about 3 days and the inflorescence was 5 days.(2)Pollen had vigor after the 1-18 h of anthesis.Stigma was receptive after 48 hours of anthesis.The out-crossing index was 4,P/O was 1 450-2 250.The breeding system of five species were given priority to out-crossing,part self-compatibility,insects pollinator dependent.(3)Eristalis cerealis and vespa ducalis are effective pollinators.The visiting frequency showed triple-climax was 10:00-12:00 and the visiting time was 2-10 s per flower.