Abstract: The response for multiple coupled HVDCs can only be simulated through EMT programs. To increase the simulation accuracy, the EMT-TS Hybrid simulation has been used in studies of the power system operation. Currently, the EMT-TS hybrid simulation speed is too slow. This paper presents a novel power system tearing technology to greatly improve the simulation speed in EMT-ST network islands as many as possible, while the EMT network is teared through the combined transmission line. An algorithm is supposed to form the EMT-ST subnetwork groups, which has no coupling with each other. And the ST-EMT subnet group decoupled in a single time step base on this algorithm. Then an novel parallel program structure is proposed to use this EMT-ST subnetwork groups to realize the parallel simulation and speedup the simulation. The case studies of the grids with 7 HVDCs and 4000 nodes show that the proposed method could greatly improve the simulation speed without lowering precision.