The radiation temperature measurement system with a wide dynamic range requires different integration time and neutral density attenuators with different transmittance levels for the radiation sources exhibiting different temperatures. The attenuators and integration time often need to be re-calibrated because of their variation. The re-calibration process is cumbersome, and thus the efficiency of the whole system is reduced. First, based on the calibration theory, a radiation calibration model of the radiation temperature measurement system with a wide dynamic range is developed herein. This model considers the integration time and the transmittance of the neutral density attenuators. A simplified calibration method is also proposed to realize the calibration models of attenuators having different radiation transmittance at different integration time. Two different integration time are calibrated using the proposed method. Then, the gray value response of the system caused by internal dark current and stray radiation is calculated by calibrating at integration time of 0.8 ms and 1 ms using an attenuator having 0.0278% transmittance. Therefore, the calibration models of the attenuators having 0.0740% and 0.8193% transmittances at different integration time can be derived. The precision of temperature measurement is experimentally tested. The experimental results indicate that using the proposed calibration method, the maximum temperature measurement errors of the calibration model for the 0.0740% attenuator at integration time of 0.8 ms and 1 ms are ≤0.36% and ≤0.46%, respectively, and that for the 0.8193% attenuator at integration time of 0.2 ms is ≤4.5%. As for the proposed method, within a certain error range, the calibration efficiency is improved and a certain precision of temperature measurement is guaranteed.