This paper presents optimal design of the light-emitting-diode (LED) array for the single-loop CCM buck-boost LED driver. The exponential function for describing the characteristics of the LED is used to represent the relationship between the forward voltage and current of LEDs. Moreover, in order to analyze the system characteristics, the equivalent circuits of the single-loop buck-boost driver for the LED array are built. Considering the requirement of the system stability and maximum-efficiency power transferring, the unity quality factor is preferred for the optimal design of the LED array. In this paper, the derived transfer functions are verified with SIMPLIS® simulation results.