The junction temperature is an important parameter that affects LED performance. It is of great significance to measure the junction temperature of LED quickly and accurately for the design and performance testing of LED products. Under different driving currents, the normalized spectral distribution of the GaN-based white-light LED arrays at different substrate temperatures was measured, and the centroid wavelength was calculated. The relationship between the centroid wavelength and the average temperature of the LED array was analyzed. The junction temperature of the array was measured and compared with that measured by the central wavelength method. The results show that there is a good linear relationship between the centroid wavelength and the average junction temperature, and the slope of the straight line changes exponentially with the change of the driving current. Compared with the central wavelength method, the accuracy of this method is higher. Therefore, using centroid wavelength to measure the junction temperature of the GaN-based white LED array is an intuitive, non-contact effective method.