A light source device (01) and a control method thereof, a backlight module and a liquid crystal display device are provided. The light source device (01) comprises: a plurality of light emitting chips (011), the plurality of light emitting chips (011) including a first light emitting chip capable of emitting visible light of a first color, the control method of the light source device (01) comprising: causing the plurality of light emitting chips (011) to emit light simultaneously in order to obtain an operating visible light spectrum; obtaining a first energy ratio of the visible light of the first color in the operating visible light spectrum; comparing the first energy ratio with a target energy ratio; and adjusting the first energy ratio to the target energy ratio, in response to that the first energy ratio is different from the target energy ratio. Thereby, a problem of a higher ratio of blue light in an LED light source is solved, so as to achieve an eye-protection effect.