Abstract: Objective: The study aimed to explore the antioxidant activity and stability of Lateolabrax maculatus protein hydrolysates (LPH) in vitro. Methods: Chemical experiments were used to determine the antioxidant activity of LPH and analyze the effects of pH, temperature, metal ions (K⁺, Ca²⁺, Cu²⁺, Zn²⁺) and simulated gastrointestinal digestion on its stability. And the oxidative damage model of Caco-2 cells induced by hydrogen peroxide was used to explore the protective effect of LPH against cellular oxidative damage. Results: LPH had strong free radical scavenging activity against DPPH and ABTS and the IC₅₀ values were 2.13 mg/mL and 31.53 μg/mL respectively. LPH was stable to pH(2.0~12.0), temperature (25~100 ℃) and K⁺ (0.25~2 mmol/L). Ca²⁺ and Cu²⁺ at 0.25~2 mmol/L improved DPPH scavenging rate of LPH, while Zn²⁺ above 1 mmol/L decreased it. In addition, LPH had good gastrointestinal stability. In the Caco-2 cell model induced by hydrogen peroxide, LPH significantly increased cell viability from 58.02% to 83.40% (P<0.05), significantly inhibited the release of intracellular reactive oxygen species (P<0.05) and restored mitochondrial membrane potential to normal level. Furthermore, LPH significantly inhibited the activity of lactate dehydrogenase in supernatant to 19.34% of model group (P<0.05) and significantly increased the activities of superoxide dismutase and catalase in cells (P<0.05). Conclusion: LPH had good antioxidant activity and stability, suggesting a good application prospect in the area of functional nutritious food.