The results show that there were 4 specises of parasite in juvenile and fingerning fish which was cultured in Cu Van - Dai Tu - Thai Nguyen. This were Trichodina, Ichthyophthyrius, Dactylogyrus, Stentor. While tilapia is the most sensitive of Trichodina, grass carp is Ichthyophthyrius, Dactylogyrus and silver carp is Stentor. Fish was holded in tank as long as which lead to raising appearance of parasite. In treating, the authors should use coopersulphate to treat monoparasite and formalin for Dactylogyrus.