In 5G-advanced and 6G network, satellite communications network and terrestrial communication network will be integrated, which is capable of providing global coverage and supporting large-scale user access. In integrated satellite-terrestrial network (ISTN), users have two optional access methods, satellite access or terrestrial radio station access. To efficiently utilize resources, it is a challenging task to assist users to select the optimal access method. In this paper, we propose a dynamic selection mechanism of access strategies with the goal of minimizing user expenses, jointly optimizing the user’s energy consumption and application server resources. Simulation results demonstrate that the proposed mechanism is feasible under various scenarios.