Abstract: Abstracts: The study assessed the impact of dietary arginine supplementation on the growth performance, feed efficiency, muscle attributes, and antioxidant potential of Songpu mirror carp (Cyprinus carpio Songpu) during the mid-growth stage. Six semi-refined diets containing 28.11% crude protein were formulated with dietary arginine levels of 0.71%, 1.06%, 1.41%, 1.76%, 2.11%, and 2.46%. Each diet was fed to three replicate groups of carp with an initial body weight of (298.89±15.30) g for 56d Results indicated that the weight gain rate (WGR), specific growth rate (SGR), and protein efficiency ratio (PER) exhibited an initial increase followed by a decrease as arginine levels in the feed rose, with the most pronounced enhancement occurring at 1.41% arginine. Conversely, the feed conversion ratio (FCR) demonstrated an opposite trend, showing significantly lower FCR (P<0.05) in the 1.41% group compared to the other groups except the 1.76% group. In the 1.41% arginine group, value in hardness, elasticity, chewiness, and shear force metrics were superior to the other groups. Furthermore, water loss rates for centrifugation and cooking in the 1.41% arginine group were the minimal and centrifugation water loss was significantly lower than those in the 0.71% and 2.46% groups (P<0.05). However, cooking loss rates did not vary significantly amongst groups (P>0.05). Myofibre diameter was notably reduced (P<0.05) in the 1.41% arginine group compared to those with 0.71%, 2.11%, and 2.46%, whereas myofibre density was significantly augmented (P<0.05) in other groups except for the 1.76% group. For muscle color, L^* value in the 1.76% group and b^* value in the 1.41% group were significantly lower than those in other groups (P<0.05). The a^* values exhibited an increasing trend, and highest value occurred in the 1.41% group (P>0.05). The activities of superoxide dismutase (SOD) and peroxidase (POD), catalase (CAT) and contents of glutathione (GSH), and total antioxidant capacity (T-AOC) were significantly elevated (P<0.05) in the 1.41% cohort in contrast to the other groups, whereas malondialdehyde (MDA) content in the muscle reached the lowest level in the 1.41% group, showing no significant differences (P>0.05). The expression of rapamycin target protein (tor), protein kinase B (akt), S6 protein kinase 1 (s6k1), 4E-binding protein 1 (4ebp1), and forkhead box O1 (foxo1) was substantially upregulated in muscle in the 1.41% arginine group (P<0.05). Based on WGR, SGR and FCR as evaluation indexes, binomial regression model analysis showed that dietary arginine requirements for Songpu mirror carp in growth mid-stage were 1.41% to 1.58% of feed dry matter.