Erectile dysfunction is categorized as psychological, organic and mixed. Generally, the causes are clarified through laboratory tests, penile hardness test with audio-visual stimulation, penile nocturnal erection test, penile cavernous injection vascular drug test, penile color Doppler ultrasound blood flow test and penile cavernography. 1. Laboratory tests: including routine blood tests, sex hormones, blood sugar, blood lipids and thyroid function. 2. Penile hardness test with audio-visual stimulation: It is used to stimulate and induce the response of penile erection through audio-visual materials and measure its hardness for preliminary screening. 3. Nocturnal penile erection test: It can identify psychological or organic erectile dysfunction. 4. Penile cavernous injection vascular drug test: usually used to assess vascular function, suitable for patients whose etiology is difficult to identify. 5. Penile color Doppler ultrasound blood flow test: to detect the arterial and venous blood flow of the penis 6. Penile cavernography: usually used for the diagnosis of venous erectile dysfunction. If there are uncomfortable symptoms, you should consult a doctor for examination to make a clear diagnosis.