The Spatial reuse Time Division Multiple Access (STDMA) ad hoc network got applied in the marine navigation realm. The resulted system, Automatic Identification System (AIS), has been extensively used in marine industry. It well serves the surveillance and communication purposes for marine navigation, and makes a great improvement on marine technology. Throughput is an important measure to such a surveillance and communication system, especially with the rapid increase of the amount of ships and their speed. In this paper, we firstly find out the influence factors of throughput through analysis of the system?s basic principle. Through simulation, we simulate and analyze how these factors impact the throughput performance. Finally, we simply propose some suggestions for improving it within different environment.