The invention discloses a new water mildew-resistant salmon trout construction method, and relates to a new disease-resistant salmon trout construction method. The method can be used to reduce salmon trout loss caused by water mildew without using a lot of disinfectant or antibiosis medicament, thereby raising salmon trout quality. The method comprises the steps of 1 establishing a basic seed selection group; 2 establishing family systems in the number of N; 3 weeding out; 4 secondary water mildew infection; 5 breeding to establish filial generation family systems in the number of M; and 6 repeating steps 1 to 5 until water mildew-resistant property is stable. According to the invention, beneficial colony heredity variation is utilized, and new disease-resistant species or lines are cultivated through fertile breeding; the new species has good heredity of disease resistance is stable; the appearance of the fish as a goods is prevented from being damaged due to water mildew; and mortality caused by water mildew is reduced to 30% below.