The utility model provides a full inner reflection color combining prism which is agglutinated by seven prisms and forms a first, a second, a third, a forth and a fifth interface, a first, a second and a third surface, a first, a second and a third incidence plane, and an exit surface. The forth interface makes red light and green light to pass through and reflects blue light; the fifth interface makes blue light and green light to pass through and reflects red light; the red light, green light and blue light input respectively from the first, the second and the third incidence plane are reflected respectively by the first, the second and the third interface and are transmitted out from the first, the second and the third surface. The image input from the first surface is reflected by the fifth interface and is output from the exit surface; the image input from the third surface is reflected by the forth interface and is output from the exit surface; the image input from the second surface directly passes through the forth and the fifth interfaces and is output from the exit surface.