Abstract: The existing designs of space-to-ground single-photon communication have the defect that the system-level parameters are difficult to be given, due to the adoption of the analysis based on subsystems. For the purpose of combining all subsystems and key system-level parameters’ influence, full-link simulation method is introduced. A space-to-ground optical communication full-link simulation system based on OMNeT++ is constructed to perform the APT (Aiming, Pointing, Tracking) and single-photon communication experimentation by Monte-Carlo method. The simulation system has the abilities of simulating correlations between subsystems, reflecting the key parameters’ influence on the whole system, and estimating the performance of a true system due to its full-link character. The simulation system is significant to design and optimize true space-to-ground optical communication systems.