【Abstract】 Objective To study the actual dose changes of bladder in the treatment of cervical cancer and the effect on the target area according to bladder filling degree in patients with intensitymodulated radiotherapy, and provide a basis for accurate evaluation of bladder dose and bladder preparation before radiotherapy. Methods From January 2019 to December 2019,10 cervical cancer patients with intensity-modulated radiotherapy were selected. The bladder and the target area were delineated by the same radiotherapy doctor on the CT and cone beam CT (CBCT) image. The changes of bladder centroid and its dosimetric change parameters were compared and the reasons were analyzed. The volume of missed radiotherapy target area was counted under different dose conditions. Results With the increase of bladder volume, the correlation coefficients of bladder centroid with superior inferior and anterior posterior directions were 0.964,-0.678, and all had statistically significant (P＜0.05). The correlation coefficient with leftright direction was -0.165, and without statistically significant (P=0242). With the increase of bladder volume, V30, V40, V50  and Dmean  had decrease trend, the correlation coefficient was -0.872,-0.805,-0.593,-0.795, and all have statistically significant (P＜0.05). As the bladder volume changed more than 200mL（P＜0.05）, the volume of missed radiotherapy target area was obvious increased. Conclusion The consistency of bladder filling degree in patients with cervical cancer during radiotherapy is poor, resulting in the change of target displacement and bladder irradiation dose during actual treatment. Therefore, the urine volume of patients should be recorded before radiotherapy positioning. Before treatment, the urine volume should be measured by bladder volume meter, and the change of bladder volume relative to positioning should not exceed 200ml.