Based on a large amount of test data, the variations of the output gray value and the calibration background bias of an infrared measurement system with ambient temperature were analyzed. Further, the influence of background bias on the precision of the surface target-radiance measurements was assessed. Based on the results, a new method for calculating the surface target radiance based on background offset cancelling is proposed. This method can improve the measurement accuracy of the infrared radiation characteristics of dynamic targets by eliminating the influence of background bias, which is influenced by ambient temperature. The dynamic characteristics of a particular type of aircraft were calculated and compared using both the traditional and the proposed methods. The results verify the effectivity of the newly proposed method.