The structure and working principle of a freeform LED concentrator were researched and a compact LED concentrator with refractive and reflective freeform surfaces for the micro-projector was designed to improve the concentration efficiency and to compress the volume. Based on non-imaging optics and the method of simultaneous multi-surfaces, the curves of freeform surfaces in the meridian planes were calculated, then the 3D structure of the concentrator was obtained by rotating the curves along Z axis. The simulation result confirms that the concentrator can collect the energy from high power LED sources effectively with a collection efficiency of 71% and can control the divergence angle within 12°.compared with conventional reflective ones, this new concentrator increases the collection efficiency by 20% and compresses the volume by 70%. The design can provide a reference for the microminiaturization of LED micro-projectors.