Objective To analyze the difference of the cumulative dose of different dose superposition methods in cervical cancer internal and external radiation, and evaluate the accuracy of direct superposition method. Methods The radiotherapy plan of 10 patients with cervical cancer who received internal and external irradiation was retrospectively analyzed. With the deformation registration method in the MIM software, the fractional internal radiation dose and external radiation dose of each patient were superimposed and compared with the direct superposition method. Results When superimposing the fractional internal radiation radiotherapy dose, it was found that the average values of the tumor target area D90%, bladder D2cc, and rectum D2cc obtained by the direct superposition method were 6.54, 1.66, 4.05 Gy higher than the results of the deformation registration method, and there were statistical differences (P＜0.05). When the internal and external radiation doses were superimposed, it was found that the average values of the tumor target area D90%, the bladder D2cc, and the rectum D2cc obtained by the direct superposition method were 5.35, 0.78, and 6.72 Gy higher than the results of the deformation registration method, and tumor target area D90% and rectum D2cc were statistical differences (P＜0.05), bladder D2cc was not statistical differences (P＞0.05). Conclusion The normal tissue dose assessed by direct superposition method is too high, it may be appropriate to relax the actual work conditions.