Abstract: Ichthyophthirius is ornamental fish breeding common disease,disease treatment,if not in time, the mortality rate is as high as 90% above.Through the malachite green of Japanese kio＇s Ichthyophthirius disease treatment brocade carp test and malachite green brocade carp to Japanese kio the toxicity tests, comparing the different concentrations of malachite green disease effect and the melon toxicity, and the result shows that： 80 minutes of malachite green half to death of Ichthyophthirius mass concentration 0.47mg/L.