Abstract: Based on the introduction of the overall design considerations for the spacetoground optical communication link, the research on some important concepts, such as parameters’coordination in the design of communication link, effect of atmospheric channels on system design, design of communication subsystem, subsystem design of beam APT (acquisition, pointing and tracking) , optical system design and so on, involved in the design process,is discussed in this paper. All the work we did would help us to know the spacetoground optical communication very well and realize it ultimately.