Qingfengmycin is an antibiotic produced by Streptomyces qingfengmyceticus.The antibiotic can inhibit the growth of Myxobacteria and thus it can be used as a fineprophylactic and therapcutical agent for gill-rot fish disease infected by pathogenicMyxobacteria on black carp (Mylopharyngodon piceus) and grass carp (Ctenopharyn-godon idellus). The better way of treatment is to feed the sick fishes with theantibiotic mixed with food. The therapeutical dosage of qingfnegmycin for adult fish was 2.5 million unitsper 50 kilogram body weight daily. The recovery rate was 95% when the drug wasapplied succesively for three days. For young fish a dosage of 5 million units per 50kilogram body weight was applied and the recovery rate was 72.7%. If both adult andyoung fish were given a prophylactic treatment with the antibiotic before the epidemicseason it was found that the mortality of the treated adult fish was 1% while 27% inthe control. The mortality of the treated young fish wag 15.7% while 40.3% in thecontrol. Qingfengmycin can be produced by conventional solid fermentation method.Morever, the material which used as culture medium for the Streptomyces can also beused as additional fish food. The antibiotic is non-toxic and inexpensive.