Catheterization is usually performed through the steps of vulvar disinfection, insertion of catheter and fixation of catheter. 1. Sterilization of the vulva: the patient should lie on his back, exposing the genitals, and the doctor will routinely sterilize the genitals and the surrounding skin. 2. Insert the catheter: (1) men: after routine vulvar disinfection, first hold the penis, put the penis upright catheter lubricated from the urethral orifice slowly inserted about 20 cm will see urine discharge, proving that the catheter has entered the bladder. (2) Women: after routine disinfection with the thumb and forefinger to separate the labia majora and minora, the big guy to apply lubricant. Insert the catheter slowly from the urethral opening, about 10 centimeters, see the urine discharge, proving that it has entered the bladder. 3. Fixed catheter: After the catheter is inserted into the bladder and urine is seen to be discharged, a syringe is used to inject saline into the balloon for fixation to prevent the catheter from slipping off. Afterwards, routine sterilization of catheterization is completed. Catheterization should be operated by a professional doctor.