DNA vaccine has brought new hope to tumor immunotherapy， and appropriate adjuvants can further improve the immune effect of it. In this study， the polysaccharides extracted from pleat， stem and cap of Ganoderma lucidum were isolated. The immune function promoting effects of the polysaccharides from different parts were investigated in mice model. Then the faciliting ability of the Ganoderma lucidum polysaccharide on tumor immunotherapy effect of HER2/neu plasmid DNA vaccine were investigated with the ignificant immune promoting polysaccharide. 4T1 tumor bearing mice were divided into control group， DNA vaccine group and Ganoderma lucidum polysaccharide group. Ganoderma lucidum polysaccharide group were given 30 mg/kg Ganoderma lucidum polysaccharide for 3 days before subcutaneous injection of DNA vaccine twice. After 21 days， the tumor size and weight of mice were measured. Compared with DNA vaccine group and control group， the tumor growth of polysaccharide group was significantly inhibited and the weight growth was stable. T cell phenotype and its subtype analysis showed that Ganoderma lucidum polysaccharide could significantly promote the cellular immune response of mice to HER2/neu plasmid DNA vaccine. This study will provide a theoretical reference for the development of DNA vaccine adjuvants.