Abstract: With the development of military space technology, space-based system plays an increasingly important role in the Ground Combat. According to characteristics of the space-based tactical communication network, high priority network group sites often need faster rate to get capacity for emergency data transmission, this study puts forward a suitable priority strategy for different priority needs of ground group after deeply analyzing the space-based tactics and BTDAMA protocol based on which this study establish a priority model applying to BTDAMA with combined Free and Demand (BTDAMA-FD) that is called priority BTDAMA-FD. This study particularly introduced the implementation process of priority BTDAMA-FD in OPNET Modeler software. Finally, by analyzing the simulation results via compare with the performance of standard BTDAMA-FD protocol, the simulation result can verify that the priority BTDAMA-FD has a better delay/throughput property.