Cervical cancer is among the most frequent cancer types in women worldwide. Radiotherapy, including external beam radiation and brachytherapy, is one of the commonly used treatment options for cervical cancer. However, the adverse effects of radiation therapy on cervical cancer survival have been poorly investigated with inconclusive results. Therefore, the aim of this study was to determine the suitable radiotherapy modality according to patients' characteristics. A retrospective survival analysis of 44,602 patients was performed using the Surveillance, Epidemiology, and End Results (SEER) database. Multivariate proportional hazard Cox model was used to evaluate the prognostic impact of different radiotherapy modalities, primary surgery, age, TNM stage, and tumor size. Our results indicated that patients without primary surgery, diagnosed at older age (≥45 years' old), at advanced TNM stages (III/IV) or with larger tumor size (≥3 cm) could benefit from radiotherapy. However, radiotherapy was detrimental in patients with primary surgery, diagnosed at younger age (<45 years' old), at earlier TNM stages (I/II) or with smaller tumor size (<3 cm). In addition, external beam radiation was in most cases less effective compared with combined external beam and brachytherapy. These results highlighted the necessity of realizing personalized radiotherapy treatments for patients with cervical cancer.