The miniaturization of LEDlamp with high luminous flux and light uniformity is the pursuit of LEDlighting,including commercial and civil lighting.The chips on board (COB)-LEDappeared recent years has high flux.However,special secondary optics still need to generate the required irradiance distribution.For small lighting device with compact freeform surface lens on large size COB-LED,a fast optimization design method to achieve the goal of uniform illumination in circular region is proposed.During the optimization,equal arc-length method is applied to reduce the number of optimization points,thus optimization efficiency is enhanced substantially.Combining the cubic spline interpolation and custom merit function,uniform illumination on the target area with light angle at range of 30° to 50° is realized in secondary development environment of TracePro software.The illumination uniformity and light energy utilization rate of the target plane reach more than 90% and 95% respectively.This method is also suitable for the design of uniform lens for COB-LEDpackage .