Abstract: This study investigated the effects of dietary extrusion temperature on growth performance, nutrient digestibility, waste discharge, and gastrointestinal microbiota of largemouth bass (Micropterus salmoides). Fish were fed diets containing 48% protein and 9% fat, extruded at two three-stage heating programs (D1: 100℃, 120℃, 120℃; D2: 100℃, 120℃, 140℃), in an indoor recirculating system for 63d. Compared to the D1 group, the D2 group exhibited significantly higher final body weight, weight gain rate, and specific growth rate, along with a lower feed conversion ratio (P<0.05). The D2 group also showed a significantly reduced hepatopancreas index but an increased viscerosomatic index (P<0.05). Nutrient retention efficiency of carbon and phosphorus and apparent protein digestibility were significantly improved in the D2 group (P<0.05), though apparent phosphorus digestibility did not differ between the two groups (P>0.05). While whole fish and fecal carbon, nitrogen, and phosphorus contents remained similar between groups (P>0.05), the D2 group showed significantly lower waste outputs (P<0.05). Distinct microbial communities were observed between the stomach and intestine (P<0.05), but extrusion temperature had no significant effect on alpha diversity of the digestive tract and the community structure (P>0.05). These findings suggest that moderately increasing extrusion temperature enhances growth performance and nutrient utilization in largemouth bass while maintaining microbial community stability and reducing aquaculture waste output.