The invention relates to a preparation method of an expanded compound feed for micropterus salmoides and snakehead fishes. The method comprises the following steps: weighing raw materials and conventional auxiliary materials according to a formula, mixing, grinding, and screening by an 8-10-mesh sieve to obtain roughage; performing secondary grinding on the roughage, screening by a 60-80-mesh sieve, and uniformly mixing with a formula amount of other auxiliary materials to obtain a mixture; performing superfine grinding on the mixture, and screening by an 80-100-mesh sieve to obtain superfine powder; moving the superfine powder into a blender, adding steam, with temperature of 90-100 DEG C, accounting for 14%-15% by mass of the superfine powder for blending, and processing in an extrusion and expansion granulator to form feed granules; and drying the feed granules at 95-103 DEG C to obtain the expanded compound feed. According to the method, primary nutrient indexes are optimized, the prepared compound feed is good in palatability, high in water body stability, reasonable in cost and high in feed conversion rate through popularization and application, the fed fishes are normal in growth speed, body shape and quality, and the water body pollution is effectively alleviated.