In this paper, a method for measuring the field of view of an infrared thermistor sensor, the principle of hardware, the software design method and the algorithm for auto-mearsurement are presented. The parallel light from different incoming angles is focused at different points of the sensitive element by a lens. The signals of corresponding intensity are obtained. Through frequency selection, amplification, data acquisition and data processing by the measurement system, the envelope curved surface of signal intensity and the curve of the field of view close to the ideal theoretical design value are obtained. Thus, the quality of the sensor can be evaluated and the errors caused by the deviation between the boresight of the lens and the mechanical axes of the sensor can be corrected.