The invention discloses a method for establishing an electromagnetic transient simulation model of a large-scale AC-DC (Alternating Current - Direct Current) power system. At first, an AC-DC power system network is simplified in an electromechanical transient mode by a power system dynamic equivalence method through the utilization of the electromechanical transient simulation data of the large-scale AC-DC power system; secondly, a conversion correspondence principle of an electromechanical transient element model and an electromagnetic transient element model is provided, so that the electromagnetic transient simulation model is established according to the simplified electromechanical transient simulation model of the AC-DC power system. By the adoption of the method provided by the invention, the electromagnetic transient simulation model can be established directly according to the electromechanical transient simulation data of the large-scale AC-DC power system; moreover, the dynamic characteristics of a prototype system are kept; therefore, an AC system and a DC system can be further studied in terms of detailed interaction, multi-direct-current commutation failure characteristics and recovery characteristics after direct current commutation failure.