A projection system including a light source, a color separator, a scrolling unit, a light valve, a wire grid polarization beam splitter, and a projection lens unit is provided. The color separator separates an incident beam according to color. The scrolling unit scrolls the color beams. The light valve processes an incident beam according to an image signal and forms a color picture. The wire grid polarization beam splitter is disposed between the scrolling unit and the light valve and transmits or reflects an incident beam according to a polarization of the incident beam. The projection lens unit magnifies the color picture formed by the light valve and reflected by the wire grid beam splitter and projects the magnified color picture onto a screen.