Abstract:Malachite green was the most effective drug against Saprolegniasis which is a common fungal disease and shows serious hazard in aquaculture in the past, while it was listed as banned drugs in China in 2000 for its side effects of highly toxic, carcinogenic, teratogenic, and mutagenic. However, the malachite green has factors of good anti-Saprolegnia effect, cheaper, being easy to get and lack of corresponding alternative drugs, so that privately using had occurred frequently and never stopped despite repeated prohibitions, which caused serious harm to the quality and safety of aquatic products. The drug "Mei Ting" developed by the Shanghai Ocean University shows good resistance efficacy to Saprolegnia and safety in the practice and application of many cities of China. It is of great significance to completely put an end to the use of malachite green as well as protect the quality and safety of aquatic products.