Measurement of the temperature field of heat dispersing surface of air-cooled condenser (ACC) is the basis of researching its heat transfer mechanism and characteristics. An image-matching-based temperature field measuring method is presented. Four infrared thermal imagers are used to photograph the longitudinal range, while the horizontal range is photographed by moving cleaning stand. 124 infrared images with overlay area are photographed. Geometric distortion correction is applied to the infrared images, and irradiance imbalance is removed. Characterized by centers of base tubes, the phase correlation algorithm based on gray projection is used for registration. Entire registered image is obtained with registration error less than 1 pixel. Then, based on the average grayscale of limited numbers of rows or columns in joint seams, the registered image is smoothed. Continuous temperature field image of the overall heat dispersing surface can finally be obtained with the maximum spatial resolution four times higher than that of a single image. Each pixel represents 12 mm on the surface, and a temperature measurement accuracy of ±0.4 ℃ is achieved. Comprehensive and accurate temperature distribution information of ACC can be provided by this method for the operation optimization of air-cooling units.