OBJECTIVE To investigate the application value of MRI combined PSA in prostate cancer bone metastasis. METHODS 74 prostate cancer patients were selected in our hospital, patients were tested for the serum PSA level and MRI after admission to detect the expression of prostate cancer bone metastasis. RESULTS All 74 patients in our group, the positive cases of prostate cancer bone metastasis were 43 cases (58.1%), positive cases in prostate cancer bone metastasis with PSA≥ 20 μg / L group was 69.6%, significantly higher than PSA (μg / L) ﹤20 μg / L groups 22.2%, the difference had a statistical significance, P﹤0.05. CONCLUSION PSA has a good prediction effect on prostate cancer bone metastasis. When PSA≥20 μg, the probability of prostate cancer bone metastasis increases significantly. PSA≥20 μg/L combined MRI can significantly improve the detection rate in prostate cancer bone metastasis.