Benign prostatic hyperplasia (BPH) is a progressive disease causing male lower urinary tract symptoms. The incidence of BPH increases with age. Studies have revealed that the prostate microenvironment is closely related to occurrence and development of BPH. This article reviews the mechanisms of cell components, such as lymphocytes and fibroblasts, inflammatory mediators, such as interleukins and growth factors, hypoxia and oxidative stress in the microenvironment that promote prostate hyperplasia.