Abstract: A new infrared temperature measure system based on the calorimetric method has been developed to survey the welding temperature field in real time.There is a special dual wave length optical filter set in the system,which makes it possible that infrared images with two different wavelengths can be synchronously sampled through one camera lens.The filter was built by joining of two half round filters,which are designed to have different wavlengths.The values of the dual wavelength are designed according to the requirement of the calorimetric method and are 0.805 0μm and 0.895 0 μm in this paper.By animing the joint line of the filter at the center of the welding pool,the dual wavelength infrared images of the welding temperature field can be caught with a single lens CCD camera,i.e.the two half rounds of the image are different on the wave length.Since the joint line of the filter is very narrow,the bilateral symmetrical points' gray scales of the images can be treated as dual wavelength data of the same point.In this way,the each pint's temperature of the welding field near the pool can be calculated with the calorimetric method.Based on it,the welding temperature including the fusion region can be further derived.The advantage of the system is that the infrared temperature measurement device has been simplified for practical application of measuring the welding temperature field.