The system for stabilizing wavelength of LED (light emitting diode) radiation in backlight module of the LCD (liquid crystal display) comprises two photodiodes, a plurality of LEDs, a microprocessor unit (MCU) and a driver circuit, wherein two photodiodes have different photo sensitivities in response different wavelengths. A target value, associated with a ration of photo sensitivities of the two photodiodes under two different wavelength radiations, is stored to the MCU as a referred value. Thus, another wavelength (or wavelength variation) of LED radiation is derived by comparing another target value with the referred value. The MCU determines a correction constant based on a color match function of the derived wavelength, and outputs a compensation signal to compensate LED, wherein the compensation signal is equal to multiplication of the correction constant and an original light intensity compensation signal for compensating light intensity loss of the LED.