The normal size of the prostate gland is about 3cm in length, 4cm in width and 2cm in thickness, with a volume of about 20 milliliters and a weight of about 20 grams. The normal size of the prostate in adult men is mainly measured by ultrasound, MRI and other examinations. Clinically, B-mode ultrasound is commonly used to determine the left and right, front and back, upper and lower diameter of the prostate, prostate volume = 0.52 × (the product of the three diameter line), in addition to experienced doctors can also determine the size of the anal finger test and other conditions. If the size of the prostate exceeds 20 milliliters, the prostate is considered enlarged. Causes of prostate enlargement include prostate hyperplasia, prostatitis, and prostate tumors, which need to be diagnosed in combination with the patient’s symptoms and other tests. The size of the prostate gland is one of the indicators of whether the prostate gland is normal or not, in addition to the symptoms and other comprehensive assessment of the presence of disease.