In general, static firing test is conducted before flight in order to obtain data such as thrust. pressure, temperature and strain, which show the characteristics of rocket motors. But the measured thrust of the obtained data is especially distorted by the effects of dynamic characteristics of thrust stand so that it is difficult for us to determine the exact value of peak thrust and rising time etc., which represent the performance of rocket motor. This paper, therefore. verified the causes of distortion of measured thrust, and proposed the theoretical method to estimate the true thrust from the distorted thrust. And also the proposed method was applied to virtual thrust stand using computer simulation, and showed good result. As a result of that, the proposed method was proven to be valid and applicable to estimate distorted thrust.