In order to improve the measurement accuracy of junction temperature o f AlGaInP-based light emitting diode (LED) by spectral analysis,a new method for determining junction temperature based on centroid wavelength is developed.The normalized spectral power distributions of AlGaInP-based LEDs are measured with different substrate temperatures and constant driving currents.The centroid wavelengths are calculated and the juncti on temperature coefficients of centroid wavelength are obtained,and then combined with the centroid wavelength of small driving current,the expression of junction temperature with centroid wavelength is obtained.The junction temperatures of fi ve red and five yellow AlGaInP-based LEDs are measured with the centroid wavelength method,forward voltage method,peak w avelength method and center wavelength method.The comparisons show that with the common visible light spectrometer of 1nm step,the centroid wavelength can be used to predict the junction temperature accurately,because compared wit h forward voltage method,which is demonstrated as the most accurate method,the mean error of the junction tempera tures is just 1.24℃.The relationship between junction temperature and centroid wavelength is linear for any AlGaInP- based LEDs.However,it is step size for the peak wavelength and center wavelength.The centroid wavelength is more suita ble for characterizing the junction temperature of AlGaInP-based LED.