Objective: Investigating the effects of farming region and commercial size on the nutrition and flavor quality of Scophthalmus maximus. Methods: Farming turbot of three regions, namely, Rushan, Haiyang and Suizhong, and two typical commercially available sizes, 450～750 and 750～1 250 g, were selected for this study to compare their nutrient composition and flavor substances. Used principal component analysis and orthogonal partial least squares discriminant analysis to visualize the differences between different groups and to identify the nutritional indicators in differentiate farming region and commercial size. Results: The protein and collagen content of turbot in the Rushan and Haiyang regions were significantly higher than those in the Suizhong region, and the DHA content of the large-size group in Suizhong accounted for 20.97% of the total fatty acid content, which was significantly higher than that of other groups. The muscle bitterness, saltiness and sweetness of turbot in the Suizhong area were significantly higher than those in the Rushan and Haiyang regions, and there were more volatile compounds in the Haiyang region, followed by the Rushan region and the Suizhong region. As for the commercial sizes, the collagen content of the large-size group was significantly higher than that of the small-size group. The volatile substances with higher content in the small-size group included 3-methylbutanal and propan-2-ol, etc., while the volatile substances with higher content in the large-size group included 2-methyl-1-propanol, 2-pinene and tetrahydrofuran, etc. Conclusion: Five indicators of fat, collagen, moisture content, total unsaturated fatty acids and ash were obtained based on the orthogonal partial least squares discriminant analysis to differentiate turbot from different farming regions, and to provide basic data for the evaluation of nutrition and flavor quality of farmed turbot.