At present, the incidence of prostate cancer is high and the diagnosis is difficult. The main clinical methods for diagnosing prostate cancer are rectal finger examination, serum prostate cancer specific antigen test (PSA). At present, the main methods for clinical diagnosis of prostate cancer are rectal examination, PSA test, imaging examination and prostate puncture biopsy. Rectal examination is the traditional method to diagnose prostate cancer, and it is also the simplest, most economical and lowest risk method. Seventy percent of prostate cancers occur in the peripheral area of the prostate, which is easy to detect by finger examination. However, for tumors that originate in the metastatic area, finger examination is difficult to detect. The sensitivity, specificity, positive predictive value and negative predictive value of prostate cancer diagnosis are dependent on the examiner’s experience, so the positive rate and accuracy are not high. 2. PSA test Serum PSA test is one of the serum markers for prostate cancer diagnosis, which has been used in clinical practice and is also an indicator for prostate cancer screening. When diagnosing prostate cancer by a single indicator, serum PSA is the best and most sensitive prostate cancer detection indicator, but its diagnostic specificity is low. At present, some more serum PSA indicators are derived for prostate cancer diagnosis, such as: PSA density, migratory zone PSA density, age-specific PSA, PSA rate, free PSA and other indicators. 3.Imaging examination Rectal finger examination and serum PSA examination are mostly applied to the screening of prostate cancer, while imaging examination is mostly applied to the diagnosis and staging of prostate cancer. Imaging examinations are mainly used to detect the lesions of prostate cancer. Currently, the main examination methods include transrectal ultrasonography (TRUS), magnetic resonance imaging (MRI) and magnetic resonance spectroscopy (MRS). In addition, tests such as CT, MRI, TRUS, PET, and isotope scan can determine the extent of prostate involvement. Transrectal ultrasonography (TRUS) is the least expensive imaging test for prostate cancer diagnosis in China. Plus, the application of color Doppler and energy Doppler can show the blood supply of the tumor in a non-invasive way. In addition, with the continuous development of ultrasonography technology in recent years, it has become possible for ultrasonography to show the blood perfusion of the prostate. MRI and MRS are used to diagnose prostate cancer, the former mainly for observing morphological signal changes and the latter for chemical shift spectroscopy. In addition, the combined application of MRI and MRS is the most ideal method to diagnose prostate cancer at home and abroad. 4.Prostate puncture biopsy Various diagnostic methods of prostate cancer ultimately need to be confirmed by pathology, therefore, prostate puncture biopsy is one of the most important methods for clinical diagnosis of prostate cancer. The guidance methods of prostate puncture biopsy include rectal finger examination guidance, transrectal ultrasound guidance, transperineal ultrasound guidance and MRI guidance. MRI guidance requires special guidance equipment and needles, thus limiting its application. Transrectal ultrasound guidance and transperineal ultrasound guidance are real-time, relatively safe, and can detect the entire puncture process without the need for complex instruments and without special requirements for puncture needles, thus becoming the most commonly used guidance puncture methods. At present, the most effective method for diagnosis with fewer complications is the 6-point method of prostate puncture, but increasing the number of puncture needles also increases the risk of complications. The limitations and development trend of prostate cancer diagnosis Because of the small size of the prostate cancer lesion and the multifocal growth of the lesion, it makes the early diagnosis difficult. Ultrasound examination will play an increasing role in the diagnosis of prostate cancer: 1) Development of ultrasonography. Ultrasonography has started to be used in clinical practice, but its relatively short duration in the prostate makes diagnosis difficult, but with the continuous development of ultrasound contrast agents and improvement of contrast technology, it is believed that it will play an increasing role in the diagnosis of prostate cancer. 2) Improving the resolution of transrectal ultrasound. With the continuous progress of ultrasound acoustic technology, the resolution of ultrasound probe is gradually improved to achieve the discrimination of small lesions, which obviously improves the positive rate of prostate cancer diagnosis. (3) The continuous progress of ultrasound imaging technology, including new ultrasound techniques like elastography and three-dimensional ultrasound will continue to play a role in the diagnosis of prostate cancer.