Abstract: The situation and the problems of the laser source used nowadays for measuring the performance of laser receivers are presented, and a novel laser source for target simulation based on a bunch of singlemode fibers which produces a laser field transmitted in Gauss distribution with settled divergence is proposed. The problems of uniformity and small divergence for reconstructing the light field distribution of target simulating laser under the condition of micro peak power density was solved with this method theoretically. The testing result of the target simulation laser consists with the actual working wavelength and width of the receiving system. The detection system developed by us has been used for quality control of laser range finders.