For weakening or eliminating the effect on uniformity, the method of uniform light accumulation based on fly-eye lens was presented. At first, illumination uniformity is designed for one LED. Then the same uniform light spot can be generated on the target surface from every LED, according to the study of LED position error. Next, An exposure light source is designed by a simulation optimization software. The maximum illuminance is 18.2 mW/cm2 while the uniformity is 86.9%, which meeting the exposure requirements fully. At last, an experiment is made to test the illumination uniformity with the method of blocking LEDs. The result shows that a few invalid LEDs cause less than 1% decease of uniformity. Even half of invalid LEDs lead to a result that uniformity declines by less than 5%. Thus, this method better suits actual manufacture than others by maintaining illumination uniformity for a long period.