The depth of insertion of the urethra in female patients is 8 to 11 centimeters. Female urethral anatomy differs from that of men in that the urethra travels from the neck of the bladder to the vestibule, and the urethra is wide and short, with an average distance of 4 centimeters, with the majority ranging from 3 to 6 centimeters. The commonly used catheter is a double/triple lumen single bladder catheter, with the balloon expanding from the posterior edge to the most anterior end of the catheter about 5 cm. The balloon serves to hold the catheter in the bladder cavity, with subsequent catheters in the urethra. Female patients are required to have a catheter inserted preoperatively for urologic surgery or other procedures. According to the length of the female urethra, the length of the catheter inserted into the urethra needs to be 9 centimeters on average, and most of them need to be between 8 and 11 centimeters, which can be injected from the water-filled lumen to inflate the balloon to fix the catheter and prevent it from falling off. Female urethra is wide and short, sphincter ability is poor, easy to cause retrograde urinary tract infection, so catheterization should be strictly aseptic operation, please by professionals.