Objective: To optimize the subcritical water extraction process for flavonoids from Mentha haplocalyx Briq. (mint) and assess the mitigating effects of peppermint flavonoids on H2O2-induced adrenal pheochromocytoma (PC12 cell) injury in rats. Methods: The subcritical water extraction process for mint flavonoids was optimized using single-factor and Box-Behnken response surface tests. A comparison was made with reflux extraction, ultrasonic-assisted extraction, and supercritical CO2 extraction methods. In vitro cell culture of PC12 cells was employed to establish an H2O2-induced PC12 cell injury model. The neuroprotective activity of mint flavonoids was analyzed using the MTT (methyl thiazolye tetrazolium, MTT) method. Results: The optimized extraction conditions were determined to be 142 ℃, 38 min, and 21:1 mL/g, resulting in a mint flavonoid yield of 14.07%±0.23%. This yield was significantly higher (P