For the global navigation satellite, when the two satellites which constitute an inter-satellite link are approximately in a line with the sun, generally the communication between them will be impacted by the sun transit outage. Based on the character of the native navigation satellite, this paper researched the sun transit outage impact theory, analyzed and emulated the factors which impacted the antenna noise, accomplished the link calculation. By establishing inter-satellite network topology emulate model, forecast the precise happen time of the sun transit outage. It also suggested some feasible methods to avoid the sun transit outage impact to offer reference to constitute the navigation satellite inter-satellite link project.