In this paper, a numerical model is established to describe the effect of temperature on the packaged thermoelectric power sensor in different environments. The thermal conductivity of the GaAs substrate and the Seebeck coefficient of the thermopiles both change with the surrounding temperature and then influence the output voltage of the sensor. The return loss of the packaged power sensor is measured to be −20dB at 10GHz and close to −12dB at the edge of X-band. The temperature experiment is performed from 273K to 363K in the temperature chamber. An agreement between the measured results and the presented model is obtained and the temperature dependence factor is close to 0.15mV/K at 10GHz under the incident power of 50mW. Furthermore, calibration of the output voltage is accomplished from 273K to 363K and the compensated power with respect to the surrounding temperature is also recorded under 50mW.