Abstract: The paper aims to study the effects of drugs that inhibit and kill pathogens, including Chinese Medicinal herbs that inhibit hyphae growth and anti- Saprolegnia agents that inhibit zoospore. The authors chose 6 commonly used anti- Saprolegnia agents (such as hydrogen peroxide, formaldehyde et al. ) and 16 Chinese medicinal herbs (such as Fructus kochiae Scopariae, Cnidium monnieri et al.) and 2 compound prescriptions (T1 and T2), used the method of spore counted and agar plate to conduct the research. The results show that hydrogen peroxide and formaldehyde inhibit spore better than malachite green, but the inhibitory effect of JiankeⅠ, sodium nitrite and peracetic acid are less than malachite green. The pomegranate rind and compound T1 can effectively inhibit the hypha growth; Fructus kochiae Scopariae, Cinnamomum cassia Presl, Citrus limon, Radix Sophorae flavescentis, Allium sativum, Polygonatum sibiricum, Foeniculum vulgare and Acorus calamus have almost no inhibitory effect on the strain; Scutellaria baicalensis Georgi, Reynoutria japonica Houtt, Lonicera japonica Thunb, Cortex meliae, compound T1, Cnidium monnieri, Pseudolarix kamepferi Gord and Rheum palmatum have better inhibitory effect. The experiment provides theoretical basis for screening the medicines which have the efficacious antibacterial activity on Saprolegnia in Oncorhynchus masou masou and developing scientific and effective utilization method of anti-Saprolegnia agents.