Small temperature variations carried by the turbulent velocity field in the Earth's atmosphere produce small phase perturbations in laser beam propagating through it. Perturbations in the phase cause wave-front errors and may significantly decrease the Strehl ratio of the laser beam. For compensation of atmospheric distortions, adaptive optics systems are used. Before the design of any adaptive optics system, the simulation of the atmospherically distorted laser beam is important. In this work, we describe the purpose, theory, implementation, and results of a wave optics propagation simulation code LAtmoSim and we investigate the effect of laser system parameters on the degree of the wave-front error caused by turbulence.