Under normal conditions, the ureter of the bladder wall segment is about 1.5~50px long, and its muscular layer and bladder muscular layer together form the Waldeyer sheath and Waldeyer gap, which has the effect of preventing bladder urine reflux, while the retention of double J tube can destroy this anti-reflux mechanism and cause vesicoureteral reflux. Normal renal pelvic pressure is about 0.978 to 1.467 KPa (1 KPa = 254.9999999999999997pxH2O), and when the pressure in the bladder exceeds the pelvic pressure, vesicoureteral reflux is inevitable. It has been measured that urinary reflux can reach the level of the renal pelvis when the pelvic pressure increases by more than 1.96KPa during voiding. In this paper, it was found that after the double J tube was placed, the vesicoureteral reflux may occur in the upright position, the horizontal position, and the head-low-foot-high position in the resting filling state of the bladder, and the average incidence of various positions is 40%. Most of the patients with vesicoureteral reflux had the contrast medium refluxed to the middle and lower ureter, rarely entering the renal pelvis, and none of them reached the renal calyces. During urination in the upright position, the rapid increase in bladder pressure caused vesicoureteral reflux in most patients, with an incidence of 95% and a severe degree. After urination, the contrast medium gradually empties from the renal pelvis and ureter, and the emptying time is related to the severity of the reflux. Most patients empty the contrast medium to the level of the resting standing position within 3 minutes. The three cases with emptying times longer than 3 minutes were all patients who had tubes placed during open surgery and had severe reflux. It is considered that this may be related to the more severe damage to the ureter from open surgery, which results in more disruption of the vesicoureteral anti-reflux mechanism. We believe that changes in intravesical pressure after placement of the double J tube have a more significant effect on vesicoureteral reflux than changes in patient position. In order to prevent the occurrence of vesicoureteral reflux after catheter placement, the duration of indwelling catheter should be prolonged in postoperative patients to keep the bladder always in a state of void and low pressure, and antibiotics can be used appropriately to prevent and treat possible urinary tract infections. After removal of the catheter, the patient should be instructed to urinate in the standing position as much as possible to prevent holding urine and avoid excessive force during urination to slowly increase the internal bladder pressure. For unstable bladder, calcium channel blockers or anticholinergic drugs can be used to relieve the uninhibited contraction of the bladder. In addition, prevention and treatment of constipation, cough and many other factors of increased intra-abdominal pressure are also important measures to reduce vesicoureteral reflux.