In this study, the dorsal muscle of prefabricated Channa argus was used as the research object, and the changes in temperature distribution, degree of doneness, sensory score, texture and water molecule distribution in the muscle under microwave heating at 160, 320, 480, 640 or 800 W were analyzed. The microwave cooking process parameters of prefabricated fish fillets were optimized. The results showed that the fish flesh were fully done at 70~80 ℃ under the microwave power of 160, 320, 480, 640 or 800 W. Through the measurement of degree of doneness and sensory evaluation, the optimal cooking time at different microwave powers (from low to high) were at 8, 6, 4, 3 and 2 min, respectively, with the corresponding minimum shear force being 67.85, 51.9, 63.70, 71.39 and 66.44 g. With the steady increase of the sample surface’s temperature, muscle protein denatured, the ability of muscle to bind water decreased, the proportion of free water continued to increase, and the shear force of fish flesh overally increased first then decreased. Based on the results of doneness degree, sensory score, texture analysis and water molecule distribution, the microwave treatment at 640 W for 3 min made the fish flesh fully cooked, the shear force the highest, the tenderness of the fish flesh the most popular, and the sensory score the highest. Thereby being the most suitable microwave cooking parameters for prefabricated Channa argus fillets.