The increasing multimedia traffic and limited spectrum resource in Geosynchronous (GEO) satellite systems starve for an efficient Call Admission Control (CAC) scheme, which aims to provide acceptable Quality of Service (Qos) to massive users, however, the throughput may not be guaranteed. In order to maximize the total throughput of communication system, a dynamic CAC scheme, named Maximizing Throughput Call Admission Control (MTCAC), is proposed. This scheme ensures the requirements of users' transmission delays while some objective conditions, such as link quality and co-frequency interference, are taken into consideration. The simulation result shows that the performance of communication system could be improved by the scheme proposed.