A mathematical model for the spectra of monocolor light-emitting diodes (LEDs) and phosphor-coated white LEDs at different drive currents is established. The simulation program of the color rendering of a white light LED cluster is developed based on this model. The program can predict not only the spectral power distribution and color rendering index (CRI), but also the number of LEDs, drive currents, input power, and luminous efficacy of a white light LED cluster at a given color temperature according to the requirement of the luminous flux. The experimental results show that the relative spectral power distributions (SPDs) and chromaticity coordinates of the model LED are very close to that of the real LED at different drive currents. Moreover, the correlated color temperature (CCT), CRI, special color rendering index (R9) luminous flux, input power, and luminous efficacy of the white light LED cluster predicted by simulation are also very close to the measured values. Furthermore, a white/red cluster with high rendering (CCT = 2903 K, CRI = 91.3, R9 = 85) and a color temperature tunable warm-white/red/green/blule LED cluster with high rendering (CCT = 2700?6500 K, CRI > 90, R9 > 96) are created.