To perform electromagnetic transient calculation on power systems, the equivalent simplification of original system should be carried out. In the electricity market environment, due to trade secrets, the relevant practitioners may not have external network information, or do not have software modules for equivalent simplification of large-scale power system, which brings difficulties to engineering calculation. A method to implement Ward equivalent based on power flow calculation and short circuit calculation is proposed. First, the currents from internal network to boundary nodes are treated as equivalent injection currents of boundary nodes. Then the node voltages and short-circuit currents are obtained by short-circuit current calculation of the boundary nodes of original system. Finally, the equivalent system parameters are calculated by node voltage equation. Theoretical analyses and results of an actual system simulation show that this method has high accuracy. This work is supported by Science and Technology Project of State Grid Corporation of China (No. 52466F150007).