Objective: To investigate the antioxidant stability and protective effect on L929 from H2O₂-induced oxidative damage of low hydrolysis degree (SCP-L) and high hydrolysis degree (SCP-H). Methods: The hydroxyl radical scavenging rate was used as the evaluation indicator for exploring the influence of temperature， pH， food ingredients， metal ions， simulated gastrointestinal environment on the antioxidant stability of sea cucumber peptides. The oxidative stress model of L929 cells induced by H2O₂ was established， and then the cell survival rate， antioxidant indicators at the cellular level were measured. Results: In the range of 20-100 ℃， both SCP-L and SCP-H have good thermal stability. The antioxidant activity was decreased in the presence of NaCl， Cu2+， Zn2+， alkali， and simulated gastric environment， while increased in simulated gastrointestinal environment. Additionally， SCP-L and SCP-H in the mass concentration range from 0.2 to 0.8 mg/mL significantly promoted the survival of L929 cells suffering from oxidative stress. Compared to the model group， the LDH activity of SCP-L and SCP-H at 0.6 mg/mL was significantly decreased by 20.67% and 25.91%， the MDA content was significantly decreased by 26.39% and 44.36%， the SOD activity was significantly increased by 89.63% and 130.17%， and the GSH-Px activity increased by 26.22% and 40.41%. Conclusion: Sea cucumber peptides should avoid contact with NaCl， Cu2+ and Zn2+ and alkali environment during storage process. Both SCP-L and SCP-H can effectively prevent H2O₂-induced oxidative damage to L929 cells， and SCP-H treatment showed better antioxidant effect than that of SCP-L.