In the modern world of telecommunications, the concept of wireless global coverage is of the utmost importance. However, real global coverage can only be achieved by satellite systems. Satellites communication is the most important mean of the communication network. The traditional satellites communication and inter-satellites links are built by microwave. In recent years, laser links for inter-satellites communication are becoming more and more important. Laser communication systems operate in a frequency range above the regulated spectrum. Laser provides many advantages for using in point-to-point ISLs (inter-satellites links) such as for links between satellites and spacecraft in deep space. Such advantages include: high speed; high bandwidth; small antenna size; narrow field of view; and narrow antenna beam. These advantages combined with the advantages in fiber optic components (optical preamplifiers, multiplexers, detectors, etc) have made laser attractive for laser links. Now we can bring WDM (wavelength-division multiplexing) to emerging broadband satellite communication systems. By using the common antenna system and ATP (Aiming, Tracking and Pointing) system, the satellites will get more capacity. In the inter-satellites laser communication, the important performances of the systems such as BER and BL both have direct relation with the optical systems. The optical systems have the function of ATP. The optical antenna is the most important component of the optical system. So the optical antenna is an important key technology to the inter-satellites laser communication. In this paper, we mainly study the optical system in the inter-satellites laser communication. we compare with three kinds of optical antennas: refractor and reflector and Catadioptrics of the passive optical system; we also analyze the effect of bandwidth to the WDM communication systems; we use the correlative software, simulate the curves of the performance of the optical antennas. These analyses will be the base of the system of WDM laser inter-satellites communication.