The invention relates to a temperature detection method of a thermofusion welding machine. The detection method comprises the steps that a) after the temperature of an indicating hot plate of the welding machine reaches a nominal temperature T, a heating surface at one side of the hot plate is shot in a thermal imagery manner to obtain a thermal image; b) a point of the highest temperature in the thermal image is selected as the high temperature feature point, and according to the position of the high temperature feature point in the thermal image, temperature measurement is carried out at a corresponding position in the heating surface to obtain the temperature TH of the high temperature point; or/and a point of the lowest temperature in the thermal image is selected as the low temperature feature point, and according to the position of the low temperature feature point in the thermal image, temperature measurement is carried out at a corresponding position in the heating surface to obtain the temperature TL of the low temperature point; and c) the temperature uniform feature of the hot plate of the welding machine is obtained according to the nominal temperature T, the temperature TH of the high temperature point or/and the temperature TL of the low temperature point. The practical temperature distribution state of the heating surface can be reflected, and the workload of measurement is reduced.