The normalized spectral power distributions of the LED arrays with various substrate tem-peratures and 350 mA drive current were measured, the centriod wavelengths were calculated, and then the relationships between the centriod wavelength and the change in the average junction tem-peratures of LED arrays were analyzed. Finally, the accuracy of the new method was studied. The results show that the centriod wavelength measured with spectrometer of 1 nm step changes linearly with the variation of average junction temperature, and the linearity is much better than that of the proposed center wavelength method. Moreover, the precision of estimating the junction temperature with the centroid wavelength is much higher. Therefore, the centroid wavelength test would be an ef-fective method to determine the average junction temperature of AlGaInP-based LED array.