A novel method is proposed to predict the spectral power distributions (SPDs) of individual emitters in a high-power laser diode (LD) array. The proposed method deconvolutes the SPD of an LD array by taking into account the thermal cross-talk effect as well as the current competition effect. A complete analytical expression to deconvolute the SPD of an LD array is described. The expression contains four key parameters that are to be measured experimentally: (1) the normalized SPD of the central emitter, (2) the temperature coefficient of wavelength, (3) the current competition constant, and (4) the maximum power of the center emitter. The method is implemented with a commercial water-cooled high-power LD array. The SPD of the LD array predicted from the SPDs of individual emitters are compared with the experimentally measured SPD of the LD array. The results show excellent agreement in both shape and magnitude, which corroborates the validity of the proposed method.