The invention provides an electromechanical-electromagnetic hybrid simulation network splitting method and device for boundary point clustering decoupling, which comprises the following steps: determining an electromechanical-Electromagnetic net dividing boundary points according to a topological structure of the power grid to be subjected to hybrid simulation; Dividing a to-be-mixed simulation power grid into an electromechanical transient network and an electromagnetic transient network according to the sub-grid boundary points; Considering the boundary point constraint, and carrying out electromechanical transient network division; Grouping the boundary points to form a plurality of electromechanical transient sub-networks and an electromechanical connection system; Dividing the electromagnetic transient network into a plurality of electromagnetic transient sub-networks and electromagnetic contact systems by adopting a distributed parameter line decoupling method and a node splitting method without considering boundary point constraints; And considering electromagnetic transient sub-network division, adjusting a grouping mode of boundary points, and dividing an electromagnetic transient calculation sub-network group to form a hybrid simulation sub-network scheme. According to the method, the real-time performance and the operation efficiency of hybrid simulation are improved.