The principle and design method of polymer optical fiber bundle (POFB) lens coupler with high-power light emitting diode (LED) as light source is studied. Based on energy compensation and coordinate iteration method, a free-form lens coupler with uniform energy distribution is designed. The lens coupler consists of two refraction free-form surfaces, two reflection free-form surfaces and a circular cylindrical lens surface. The small divergence angle of the modified Lambertian high-power LED beam is quasi-uniformly distributed on the end face of POFB through refractive free-form surface. The reflection free-form surface reallocates the energy of large divergence angle of LED beam as compensation to improve the target surface illumination uniformity. Lens coupler is designed and optimized for illumination uniformity and effective light utilization of the end face of the fiber bundle. The results of optical simulation show that when the 3535 LED is used as the light source, the designed coupler can make the illumination uniformity of the 20×20 polymer fiber bundle with the diameter of 0.5 mm reach 92% and effective light utilization reach 71%.