According to the measuring requirement for the performance measurement of pulse laser range finder with wide range, a new measuring method of laser echo signal simulation based on MODTRAN database was proposed. The laser atmospheric echo signal was simulated by detection system indoor to realize detecting of the two indexes which were the ranging precision detection and maximum range detection of laser range finder better than similar equipments. The MODRAN meteorological parameter database method was adopted to calculate atmospheric radiation transmittance of arbitration experimental in GJB2241A and mathematical model was established on this basis, FPGA and analog delay device were adopted to achieve presupposition time delay, this method made distance simulation and energy simulation becoming a close loop realizing realistic simulation of ranging laser echo signal. Experiments results show that designed laser echo signal simulator system can realize 50 m-22 km wide range distance simulation, echo delay precision is better than 2 ns, measurement accuracy of maximum range is 90% meeting the detecting demand of the ranging performance of laser range finder.