The invention relates to an infrared thermal imaging speed measuring method for an airflow filed on a building radiator hot surface. The invention aims to solve problems that the accurate and detailed measurement of the whole airflow filed in an indoor environment is difficult in point speed measurement, point-by-point measurement of the whole airflow is still very difficult and time-consuming, the shooting of continuously-distributed particles in a tested area by a PIV technology in the surface speed measuring technology is actually difficult and the operation is also complex and tedious, and further provides the infrared thermal imaging speed measuring method for the airflow filed on the building radiator hot surface. The method is achieved by a step one of selecting a proper infrared thermal imager, a step two of shooting an infrared thermal imagery video, a step three of obtaining frame images, a step four of obtaining a filtered image, a step five of obtaining the correlation between two adjacent frame images, a step six of obtaining a speed vector V by calculation, a step seven of drawing a speed vector image and the like. The invention is applied to the field of infrared thermal imaging speed measurement.