The invention relates to a broadband electromechanical-electromagnetic hybrid simulation method for a large-scale AC/DC system, belongs to the technical field of electromagnetic transient analysis ofa power system. The method comprises the following steps: initializing each state variable; dividing the system into an electromechanical subsystem and an electromagnetic subsystem; obtaining a differential equation of the electromagnetic subsystem and a differential equation of the electromechanical subsystem respectively; and then solving the differential algebraic equation of the electromechanical subsystem in a simultaneous manner to obtain the value of each state variable in the electromechanical subsystem, bringing the newly obtained state variables back to the differential equation foriterative solution until the simulation time reaches the set time, and finally obtaining the electromagnetic transient simulation result of the power system containing the power electronic unit. According to the method, the requirements for simulation precision and numerical stability can be met, meanwhile, the simulation efficiency is greatly improved, and engineering popularization and implementation are facilitated.