Autonomous underwater glider (AUG) is widely used in the long-term and large-scale marine environmental monitoring. In order to perform AUG network more efficiently, a joint mechanism of time synchronization and multiple access control for AUG (TSMAC) is proposed. TSMAC integrates the information exchange process of time synchronization and multiple access control, and it uses the glider and the beacon node to exchange information. According to the timestamp and location information required for synchronization, the clock skew and offset are calculated so as to update the local clock. Then, time synchronization is completed. The simulation results show that compared with the existing mechanisms, TSMAC reduces the number of control frame transmissions. On the basis of maintaining good throughput, the purpose of reducing the time deviation is achieved, and the energy efficiency is increased.