The transient stability of the interconnected power system connected with variable speed wind turbines will be regulated flexibly due to the controllable inertias. In this paper, the linear state equation of interconnected power system with wind turbines was derived firstly. As a new operation parameter, the impact of virtual inertia on transient characteristics of power angle was analyzed. Following that, based on the virtual inertia regulation, two control strategies adapted for the two side regional networks were proposed respectively. As a result, an improved transient stability of power angles can be achieved by coordinating the inertias between two side regional networks. Finally, a typical two area interconnected power grid with high wind power penetration was used to validate the proposed control strategies. The simulation results show that by regulating the virtual inertias of wind turbines, the transient stability of the power angle can be significantly enhanced in the interconnected power system.