To solve the archetypal problem of LED illumination:redistribute the irradiance of a given LED source or any quasi-point sources onto a desired target surface to achieve any prescribed illumination distribution,the free-form micro-lens optics is designed based on the Snell′s law and "edge-ray principle".This secondary optics can redistribute any LED radiations onto the target surfaces to achieve prescribed uniform illuminations without concerning the initial radiation patterns of LED sources.According the practical illumination requirements,the surface shape of the single free-form micro-lens can be calculated by using the ray tracing method and B-spline fitting way.Some modules of free-from micro-lens optics were constructed to achieve rectangular illumination.The simulation results show that the achieved illuminations have high uniformities and precise illuminating shapes as prescribed.The free-form micro-lens optics is applicable in LED lighting,with cogent competitive advantages.