ObjectiveTo compare the radiation dose distribution in irradiated target area and organs at risk among conventional radiotherapy, conformal radiotherapy and semi-field conformal radiotherapy in Graves' ophthalmopathy patients. MethodsThirty patients with Grave's ophthalmopathy treated between January 2010 and December 2012 were included in this study.CT scan was performed to obtain images of each patients; three-dimensional planning system (3D-TPS) was done to design conventional radiotherapy, conformal radiotherapy and semi-field conformal radiotherapy for each patient.Then, we counted the standard deviation of study parameters for each radiotherapy technique, and the results were compared among the three groups. ResultsAverage irradiation dose in target area of patients accepting conventional irradiation, conformal irradiation and semi-field conformal irradiation therapy was not significantly different (P > 0.05).V95 and the conformity index values of conformal irradiation and semi-field conformal irradiation therapy were better than those of the conventional irradiation therapy (P < 0.001), while no significant difference between conformal irradiation and semi-field conformal irradiation therapy was detected (P > 0.05).Patients accepting conventional irradiation got the highest cumulative irradiation dose in eye lens, while patients accepting semi-field conformal irradiation therapy got the lowest irradiation dose in eye lens, and the differences were significant (P < 0.05).Patients accepting conventional irradiation got the highest cumulative irradiation dose in pituitary, while cumulative irradiation dose in pituitary in patients accepting conformal irradiation and semi-field conformal irradiation therapy was not significantly different (P > 0.05). ConclusionsConformal irradiation and semi-field conformal irradiation techniques are superior to conventional irradiation technique, with a better target conformal degree and higher does distribution in target area, as well as a lower radiation dose in normal tissues surrounding target area.Semi-field conformal irradiation technique has a better performance than conformal irradiation therapy in eye lens protection.