Abstract: The in situ infrared thermometry methods of metal organic chemical vapor deposition (MOCVD) mainly include monochromatic radiation thermometry and doublewavelength colorimetric thermometry. We calculated the 940 nm and 1 550 nm spectral emissivity of 10 m GaN on silicon (111) substrate by film thickness interference model and Kirchhoffs law,compared the relative error and relative sensitivity among 940 nm monochromatic radiation thermometry, 1 550 nm monochromatic radiation thermometry, 940 nm /1 550 nm doublewavelength colorimetric thermometry within the scope of 500 ℃ to 1 300 ℃ by taking the Thomas Swan CSS MOCVD as an example,as well as the calibration betweenmonochromatic radiation thermometry and doublewavelength colorimetric thermometry.Moreover,by using the 940 nm /1 550 nm doublewavelength colorimetric thermometry,the temperature of LED epitaxial wafer with InGaN/GaN MQW structure growing on silicon(111) substrate was monitored online.The result shows that the 940 nm/1 550 nm doublewavelength colorimetric thermometry offers advantages over the 940 nm and 1 550 nm monochromatic radiation thermometry in terms of relative error and correction. The conclusion can provide reference for the in situ infrared thermometry design of MOCVD.