Airborne multi-pulse ladar target signal simulator is studied to evaluate the performance of echo signal digital processing algorithms and hardware platform. It is pointed out that only using radar equation to establish the echo waveform model is inadequate for the relationship between waveform and energy. Air target echo pulse broadening is analyzed, and the waveform time broadening data are acquired under different angles, target distances and target sizes. Because the energy remains same before and after broadening, the echo waveform mathematic model is established through solving the characteristic parameters of Gaussian pulse function. Then the simulation model based on target distance error and echo pulse waveform error statistic characteristics is given, and the method to generate echo signal according to the signal-to-noise ratio (SNR) is proposed based on the standardization of echo noise root mean square (RMS) value. The performances about echo SNR error, minimum output SNR, and continuous working time of two laser simulators are compared.