In recent years, the laser display is the tendency of the display technology. A new kind of illumination system is proposed for laser light source, which consists of laser array light source, improved Cassegrain optical system, fiber, laser diffuser and 4f-relay system. In order to obtain efficient and uniform illumination distribution, the light from the laser is collected by the improved Cassegrain optical system and then coupled into the fiber where it’s been mixed and uniformed. Then the beam is collected on the 0.61-inch LCOS chip through the 4f-relay system after being shaped by the laser diffuser. The system could achieve high brightness illumination because the fiber can be bent and combined, and the optical extension is evaluated based on optical extend. Finally, the designed system is ray tracing simulated in optical software to verify the feasibility of the method.