An optimized design method of free-form reflector surface for extended LED source, which is based on the foci mapping ellipse flow- line methods for generating free- form surfaces and the gradient operator for optimization, is presented. And a continued free- form surface reflecting the lights from a 5 mm size LED extended source to a target plane in rotational symmetrical uniform pattern is designed and optimized. Optical simulation results show that the original irradiance uniformity is about 0.77 and the optimized irradiance uniformity reaches 0.98. This method can be applied to the optical design of non-rotational symmetric reflector.