The measurement of the response of Mg2SiO4 : Tb thermoluminescent dosimeter against radiation dose has been made and the result is presented. The supralinearity observed is characterized by (1) a clear power‐law relation between the response and the dose and (2) a sharp transition from the linear to the supralinear region, a behavior which has not been found in other phosphors. A few existing models are shown to be insufficient to explain the above features. A new model seems to be appropriate.