First clean the vulva, disinfect the mons pubis and labia majora from top to bottom, then disinfect the labia minora and the external urethral opening in the same order, and finally disinfect the external urethral opening to the anus. After cleaning, check the fluency of the catheter, disinfect the vulva again, apply sterile paraffin oil on the front of the catheter, clamp the front of the catheter and slowly insert it into the urethra, insert 4-6cm, see the urine flow and then insert 5-7cm, inject 10-20ml of saline into the air sac, lightly pull the catheter with a sense of resistance, and connect it to the urine bag.