Tea polyphenols are a natural antioxidant with a wide range of biological activities, and the extraction process of tea polyphenols was optimized by supercritical extraction technology using tea dry cake as raw material, and its antibacterial properties were discussed. The extraction conditions were optimized by single factor experiment and response surface method, and the optimal process parameters were determined as follows: extraction pressure 25 MPa, extraction temperature 50°C, extraction time 90 minutes, and CO₂ flow rate 20 L/h. Under these conditions, the yield of tea polyphenols reached 15.2%. Antibacterial experiments showed that tea polyphenol extract had a significant inhibitory effect on Escherichia coli and Staphylococcus aureus, with the minimum inhibitory concentration (MIC) of 0.4 mg/mL and 0.6 mg/mL, respectively. This study provides a theoretical basis for the high-value utilization of tea cake.