A projector capable of projecting a gray-level image for adjusting a color wheel delay includes a housing, a light source installed in the housing, a color wheel, an image modulator, a control circuit, and a scalar. The color wheel separates the light from the light source into color light. The image modulator modulates the color light from the color wheel and projects the color light to form an image on a screen. The control circuit connected to the image modulator controls the image modulator to operate synchronously with the color wheel. The scalar connected to the image modulator generates a gray-level image signal. The image modulator modulates the color light and forms a gray-level image on the screen by receiving the gray-level image signal from the scalar. The control circuit adjusts the image modulator to operate synchronously with the color wheel according to the gray-level image signal.