Abstract: Saprolegniasis is a common fish disease, which causes great economic loss to aquaculture industry. In recent years, Chinese herbal medicine has become a research hotspot in the prevention and control of Saprolegniasis due to its characteristics of wide sources, low cost, safety, environmental protection, and resistance to Saprolegniasis. The author elucidated the pathogenic mechanism of Saprolegniasis pathogen, and summarized the bacteriostasis effect, extraction method, active component and safety of 60 kinds of Chinese herbal medicine from 38 families that effectively inhibited Saprolegniasis pathogen. The action mechanism of Chinese herbal medicine on Saprolegniasis pathogen was also analyzed. The results showed that Coptis chinensis Franch.,Peucedanum praeruptorum Dunn, Notopterygium incisum Ting ex H.T.Chang, Melia toosendanSieb.et Zucc., Rheum palmatum L., Sophora flavescens Alt., Syringa oblata Lindl.,Pteriscretica L. var.nervosa（Thunb.） Ching rt S.H.W,Quisqualis indica L.and Camellia oleifera Abel had significant bacteriostatic effect on the pathogen of Saprolegniasis. Acetone ultrasonic method and water decocting method were the main extraction methods. The antibacterial active components were mostly phenols and ketones. With high security, Chinese herbal medicine had little harmful effect on fish. The mechanism of action of Chinese herbal medicine on Saprolegniasis pathogen was to improve fish resistance and destroy Saprolegniasis pathogen.