Objective:To study the infiltration mode of local immune cells in prostate cancer and to explore the role of immune cells in the development of prostate cancer.Methods:Gene expression profile chip dataset of normal prostate and prostate cancer tissues were downloaded from Gene Expression Omnibus (GEO) database. The proportion of 22 immune cells in the two groups was calculated by using R and SPSS software; the differences in the proportion of immune cells between the two groups were compared. The correlation coefficients among immune cells in prostate cancer tissues were calculated.Results:The dataset GSE62872 was downloaded, and a total of 424 samples were obtained, including 160 normal prostate tissues and 264 prostate cancer tissues. There were 20 228 mRNA detected in each sample. Deconvolution algorithm was used to obtain the proportion data of 22 kinds of immune cells after data correction. The samples were screened with P < 0.01, and 63 normal prostate tissues and 57 prostate cancer tissues were obtained. The immune cells with higher expression included CD8 + T cells [(23.48±6.16)%], plasma cells [(18.46±5.74)%], monocytes [(12.15±3.82)%] and activated NK cells [(11.11±2.97)%]. The immune cells with higher constituent ratio correlation coefficient included CD8 + T cells and unactivated memory CD4 + T cells ( r = -0.609, P < 0.01), M 0 macrophages and M 2 macrophages ( r = -0.596, P < 0.01). Compared with normal tissues, the infiltration degree of M 1 macrophages and unactivated dendritic cell was increased, and the difference was statistically significant ( Z = -2.783, P = 0.005; Z = -2.129, P = 0.033). Conclusions:The infiltrated immune cells in the tumor microenvironment of prostate cancer are mainly CD8 + T cells, plasma cells, monocytes and activated NK cells. With the effect of the tumor microenvironment, M 0 macrophages mainly differentiate into M 2 macrophages cells, which may be involved in the occurrence and development of prostate cancer, providing new clues to find potential immunotherapy targets.