Abstract: To improve the extraction yield of lentinan and study its antioxidant and antibacterial activity, lentinan was extracted using hot water assisted by ultrasonic. The L9(33) orthogonal test was designed to optimized the extraction condition and the influencing factors were solid-liquid ratio, extraction temperature and ultrasonic time. The results showed that the optimum extraction condition was extracting using 90℃ water assisted by ultrasonic for 40 min with the solid-liquid ratio being 1:40. Under this condition, the extraction yield of lentinan was 6.47%. When extracting lentinan using 80℃ water assisted by ultrasonic for 20 min with the solid-liquid ratio being 1:40, the antibacterial activity was the strongest, the inhibition zone diameter of Escherichia coli was (9.95± 0.86) mm, and that of Bacillus subtilis was (8.73± 0.57) mm. When extracting lentinan using 90℃ water assisted by ultrasonic for 30 min with the solid-liquid ratio being 1:30, scavenging activity of hydroxyl radicals reached the maximum of 22.04%. When extracting lentinan using 90℃ water assisted by ultrasonic for 40 min with the solid- liquid ratio being 1:30, the antioxidant activity was the strongest. The influencing degree of the three factors was in an order of solid- liquid ratio ＞ extraction temperature ＞ ultrasonic time. The results indicated that the optimal extraction condition could improve the extraction yield of lentinan, and lentinan had antibacterial and antioxidant activity to some extent.