Abstract: The rainbow trout farming industry has gradually become a characteristic and advantageous industry in China, but in recent years, relative diseases of the fish have shown a frequent-bursting trend. Systematic disease prediction is therefore of great significance for ensuring the high-quality development of the fish farming industry. This article aims to address these challenges by categorizing and diagnosing common rainbow trout diseases for the first time, considering environmental and individual characteristics of the breeding environment, population characteristics, body surface characteristics, and anatomical characteristics. We have established 8 indicators set at each level, totaling 32 indicators in this methodology. This method is beneficial for improving the ability of farmers to self diagnose and predict diseases in advance, as well as for professional remote diagnosis and treatment. It can lay the foundation for intelligent diagnosis of major diseases of rainbow trout and further provide early warning to ensure the healthy and sustainable development of the domestic cold water fish breeding industry.