The technique of using monochromatic light-emitting diodes (LEDs) to simulate sunlight has been developed rapidly in recent years. In this research, we propose a method to improve the simulating performance based on the influence of the driving current (70 to 700 mA) on the peak wavelength of monochromatic LEDs. The largest shift of the peak wavelength was observed in the green-light LED with 9 nm deviation. A modified Gaussian formula with an additional variable, driving current I, was used to simulate the LED power spectrum, and was further employed in an optimizing algorithm to achieve solar spectrum matching by 14 types of LEDs with different peak wavelengths.