Abstract: This study systematically investigated the effects of different cooking-reheating combinations (steaming, roasting, frying coupled with water bath or microwave reheating) on the nutritional and oxidative profiles of chicken breast using orthogonal partial least squares discriminant analysis (OPLS-DA). Results demonstrated that frying significantly elevated thiobarbituric acid reactive substances (TBARS) levels compared to steaming and roasting (P<0.05), accompanied by reduced α-helix and increased β-sheet content in proteins. Fried samples exhibited lower vitamin E loss (12.90%~27.96%) and retained higher levels of key fatty acids, including C18:1n-9c, C18:2n-6c, C20:0, C18:3n-6, C18:3n-3, C22:0, C23:0, and C20:5n-3 (P<0.05). In contrast, steamed and roasted samples showed superior protein content, vitamin B₆ retention, and elevated levels of C12:0 and C20:1 fatty acids, alongside higher protein carbonyls and lower free sulfhydryl groups versus fried samples (P<0.05). Regarding reheating, microwave synergistic steam or roast reheated samples displayed significantly higher ratios of essential to total amino acids (EAA/TAA), essential to non-essential amino acids (EAA/NEAA), polyunsaturated to saturated fatty acids (PUFA/SFA), and greater retention of vitamins B₁, B₆, and E compared to water bath-reheated counterparts (P<0.05). Conversely, fried chicken breast retained higher nutritional quality when reheated via a water bath. Collectively, frying better preserves fatty acids and fat-soluble vitamins, while steaming and roasting favor protein integrity, water-soluble vitamins, and stable saturated/monounsaturated fatty acids. From the perspective of preserving key nutritional components, microwave reheating is recommended for steamed or roasted chicken breast, whereas water bath reheating optimizes fried samples. These findings elucidate the nutritional and oxidative dynamics during cooking-reheating processes, offering science-based insights that will enlighten and inform professionals about healthier dietary practices.