A solid-state volumetric true 3D display developed by Hefei University of Technology consists of a single DMD, an UHP lamp, a color wheel of RGBRGB and 240 Hz, a hollow light tunnel, 20 LC shutters, projection lens, folder mirrors, and control circuits etc., which have the disadvantages of low refresh rate and small color gamut. A LED-based illumination system is presented, comprising RGB LED modules, collimation lens, X-cube, and focusing lens to replace the UHP and the color wheel. The RGB LED modules emit RGB lights in sequence. The uniform RGB rectangular spots are produced at the end of the light tunnel. Without color wheel, the refresh rate could reach 60 Hz. The simulation and practical results show that the LED-based illumination system can completely satisfy the requirements of true 3D display.