In the present study, in order to maximize the yield of polysaccharides from Ganoderma lucidum, response surface methodology was employed to optimize the ultrasonic/microwave-assisted extraction (UMAE) conditions. The results indicated that the optimal extraction conditions were ultrasonic power of 50W, microwave power of 284W, extraction time of 701s and water/solid ratio of 11.6:1, respectively. Using UMAE, the yield of polysaccharides was 115.56% above that of classical hot water extraction (HWE) and increased by 27.7% as against ultrasound-assisted extraction (UAE), which confirmed the great potential application of UMAE technology in the extraction of polysaccharides. The immunological assays results demonstrated that polysaccharides of G. lucidum extracted by ultrasonic/microwave (UMP) could improve the weight of immune organ of immunocompromised mice, restore delayed-type hypersensitivity (DTH) reaction to DFNB, improve hemolysis antibody level and natural killer cell activity at high-dose. However, UMP had no noticeable effects on phagocytosis of monocyte at the tested dosage range.