Abstract: Objective To explore therapeutic effects of high intensity focused ultrasound(HIFU) on prostate cancer and influence on systemic T cell subsets in mice. MethodsSubcutaneous prostate carcinoma model was established by vaccinating RM-1 cells to C57BL6 mice.Model mice were randomly divided into control group, radiotherapy group, HIFU group,and HIFU combined with radiotherapy group. We calculated the growing curve of tumor and the tumor doubling time(DT). Two weeks later,CD3⁺, CD3⁺CD4⁺ and CD3⁺/CD8⁺ ratio within the total white blood cell were observed by flow cytometric analysis in diffferent groups. Results Comparing with control group, both HIFU and radiotherapy groups had slower tumor's growth and significantly longer the DT. CD3⁺(%) and CD4⁺(%) in HIFU group were higher than those in control group, and there was no significant difference between radiotherapy group and control group. The DT of HIFU combined with radiotherapy group was significantly longer than that of HIFU group, and CD3⁺(%) and CD4⁺(%) were significantly higher than those of HIFU group,moreover CD4⁺(%) was significantly higher than that of normal mice. ConclusionHIFU,especially HIFU in combined with radiotherapy,in treatment of prostate cancer not only inhibited local tumor growth, but also improved systemic cellular immunity by influencing T cell subsets.