LED cluster is probably the most relevant among the emerging solid-state lighting techniques. Impressive scenarios of a wide range of color quality and luminous efficiency have been obtained, mostly at the condition of constant ambient temperature. This paper removes the constraint in ambient temperature. We present a methodology analogous to a general lens design rule to optimize step-by-step the spectral power distribution of a white-light LED cluster. The scheme enables the users to determine the optimal operation to meet requirements such as light efficiency, color quality, or other figures of merit over a wide range of color temperatures. All main factors influencing the spectral power distribution (SPD) are discussed, alongside the implementation of a pentachromatic R/G/B/A/CW platform suitable for clinic use. The result shows the multispectral cluster can be modulated within the color temperature from 2800K to 8000K in the range ambient temperature (10°C ∼ 100°C) with high color quality scale (CQS > 85 points) and the possibly highest luminous efficiency.