We tested the host-specificity of Triangle Muessl(Hyriopsis cumingii)by infecting Yellow Catfish(Pelteobagrus fulvidraco) and Nile Tilapia(Tilapia nilotica) with its glochidia and the correlations between time course of excystment of glochidia,number of transformed juvenile and host fish species,body weight were analyzed.In addition,the plasma biochemical indexes of tilapia which were infected by glochidia of triangle mussel were determined and non-parasitized tilapia group was set up.The results showed the number of transformed juvenile from yellow catfish and tilapia per unit body weight stood at 26 435±6 430,26 327±3 091 respectively,whereas there was no obvious difference.As body weight of host fish increased,the number of transformed juvenile did actually.The peak time of detached juveniles form yellow fish and tilapia appeared at the 8th,7th day post-infection respectively with water temperature ranging from 23℃ to 25℃.In particular,the glochidia attached tilapia detached earlier than yellow fish.There were no obvious change in concentration of plasma biochemical indexes of parasitized tilapia,such as total protein(TP),albumin(Alb),glucose(Glu),total cholesterol(TC) and high density lipoprotein(HDL),whereas the concentrations of triglyceride(TG) and low density lipoprotein(LDL) significantly declined(P=0.001,0.020).There was no obvious difference in concentration of all indexes of non-parasitized tilapia either.The results will provide reference to find key factors to metamorphosis development of triangle mussel.