The work aims to analyze the effects of extraction temperature, solid-liquid ratio, extraction time and ethanol mass fraction, etc. on tea extract and study the antibacterial properties of tea extract. The active components of tea were extracted by ultrasonic assisted extraction. The antimicrobial properties and stability of the extract were analyzed by the method of paper diffusion and the double dilution method. The optimal extraction conditions of tea were extraction temperature of 70 ℃, solid-liquid ratio (ratio of tea powder mass and ethanol volume) of 1∶10 g/mL, extraction time of 30 min and ethanol mass fraction of 75%. The minimum volume fraction of tea extracts for inhibiting the growth of 4 kinds of tested bacteria was 2.5%. Within one month, the antibacterial ability was stable and kept above 95%. The tea extract has good antibacterial properties.