Fifty mice were randomly divided into control group， model group， low dose of Danggui Liuhuang Decoction group， high dose of Danggui Liuhuang Decoction group and cisplatin group （n=10）. All the mice were vaccinated with RM-1 to establish the PCa-bearing mouse models except control group.The mice in low dose and high doses of Danggui Liuhuang Decoction groups were given 0.25 and 0.50 g·kg^－1·d^－1 Danggui Liuhuang Decoction by gavage，respectively，and the mice in cisplatin group were intraperitoneally injected with 0.2 mL cisplatin. The spleen coefficients， thymus coefficients， tumor volumes and inhibitory rates of tumor of the mice in various groups were calculated. HE staining was used to observe the pathomorphology of tumor tissue of the mice in various groups. Flow cytometry was used to detect the percentages of CD4+ and CD8+T lymphocytes in peripheral blood of the mice in various groups. Western blotting method was used to detect the expression levels of programmed cell death receptor-1 （PD-1） and programmed cell death-ligand 1 （PD-L1） proteins in spleen tissue of the mice in various groups.

Compared with control group， the spleen coefficient， thymus coefficient， and percentage of CD8+ T lymphocytes of the mice in model group were increased（P<0.05），and the percentage of CD4+ T lymphocytes was decreased （P<0.05）. Compared with model group， the spleen coefficients， thymus coefficients， tumor volumes， percentages of CD8+ T lymphocytes， expression levels of PD-1 and PD-L1 proteins in spleen tissue of the mice in low dose of Danggui Liuhuang Decoction group， high dose of Danggui Liuhuang Decoction group and cisplatin group were decreased（P<0.05），and the percentages of CD4+ T lymphocytes were increased （P<0.05）. Compared with low dose of Danggui Liuhuang Decoction group， the spleen coefficients， thymus coefficients， tumor volumes， percentages of CD8+ T lymphocytes， expression levels of PD-1 and PD-L1 proteins in spleen tissue of the mice in high dose of Danggui Liuhuang Decoction group and cisplatin group were decreased （P<0.05）， the inhibitory rate of tumor and percentages of CD4+ T lymphocytes were increased （P<0.05）.Compared with high dose of Danggui Liuhuang Decoction group， the spleen coefficient， thymus coefficient， tumor volume， percentage of CD8+ T lymphocytes， expression levels of PD-1 and PD-L1 proteins in spleen tissue of the mice in cisplatin group were decreased （P<0.05）， and the inhibitory rate of tumor and percentage of CD4+T lymphocytes were increased （P<0.05）. The HE staining results showed that the tumor cells in model group were evenly and tightly distributed， with occasional vacuoles，and the tumor cells in low dose of Danggui Liuhuang Decoction group were evenly distributed and the number of vacuoles was increased， the tumor cells in high dose of Danggui Liuhuang Decoction group were loosely arranged and the number of vacuoles was increased significantly， and the tumor cells in cisplatin group were significantly reduced， and they were separated from the vacuole.

Danggui Liuhuang Decoction can improve the immune function of the PCa-bearing mice， and its mechanism maybe related to inhibiting the PD-1/PD-L1 signaling pathway.