An excitation light intensity control system, including a lighting part, an imaging part and a control part. The lighting part includes a light source; the imaging part includes a light modulator and a color conversion element; the excitation light emitted from the light source is imported to the light modulator for modulation; the modulated excitation light excites the color conversion element to produce multicolor excited light; the lighting part further includes a light recycling system used for recoupling part of the excitation light emitted from the light modulator to be incident to the light modulator; the control part includes a controller used for receiving original image data and controlling the intensity of the excitation light emitted from the light modulator and/or the light source.