Objective To explore the curative effect of implantation of radioiodine-125 particles in the treatment of patients with nasopharyngeal cancer and the application value of CT and MRI in the follow-up of patients after treatment. Methods 57 cases of patients with nasopharyngeal cancer who were treated in our hospital between January 2011 and December 2014 were included in the study. All patients were treated with implantation of radioiodine-125 particles after radiotherapy. Before treatment, the patients were examined by CT and MRI and were followed up. The CT and MRI image changes after implantation of radioiodine-125 particles were determined. Results Among the 57 cases, 12 cases were CR, 28 cases were PR, 9 cases were SD and 8 cases were PD and the total effective rate was 70.2% (40/57). After treatment, ESR decreased significantly and was lower than that before treatment (P<0.05). CT findings before and after treatment showed that before implantation of radioiodine-125 particles, the shape of nasopharyngeal cavity changed, left-right asymmetry. Nasopharyngeal soft tissues thickened or with presence of masses. The lesions mostly were nodular, thick piece lump-like or mass high metabolic; After treatment, the shape of nasopharyngeal cavity was recovered. Soft tissues became thicker or the masses disappeared; MRI findings before and after treatment showed that before implantation of radioiodine-125 particles, the main findings were presence of mixed signal and edema in nose and throat, equal or long T1 , slightly long T2 abnormal signal of nodule or mass shadow. After enhancement of fat-suppression, they were significantly enhanced. After treatment, the main feature was presence of fibrosis, complicated with edema. Conclusions The application of implantation of radioiodine125 particles under CT in the treatment of nasopharyngeal cancer after radiotherapy is of relatively better effect. To apply CT and MRI in follow-up after treatment can find changes of the lesions in time, which is of important significance in monitoring prognosis.