Abstract: In order to use copper sulfate scientifically to treat the disease caused by parasite Amyloodinium ocellatum in farmed fish, golden pompano (Trachinotus ovatus) was used as an animal model to study the copper sulfate's effective concentration and time of killing of each stage of A. ocellatum. The safety concentration of copper sulfate to juvenile golden pompano was evaluated. Results show that the juveniles had good tolerance to copper sulfate and the safety concentration was less than 43.06 mg·L⁻¹. The effective concentrations of copper sulfate to kill full dinospores within 10, 30 and 60 min were 3.13, 0.78 and 0.20 mg·L⁻¹, respectively. At copper sulfate concentrations of 2, 1 and 0.5 mg·L⁻¹, trophonts were detached from the host within 2, 4 and 8 h, respectively. However, tomonts were highly resistant to copper sulfate because they divided when being incubated with 100 mg·L⁻¹ copper sulfate solution. Additionally, the relative protection rates of pompanos infected with A. ocellatum were 80% and 90% when being immersed continuously in 0.2 and 0.4 mg·L⁻¹ copper sulfate solutions respectively for 10 d. These results imply that the immersion to copper sulfate solution can protect golden pompano from A. ocellatum infection at low concentration.