The invention discloses an electromechanical-electromagnetic transient-state hybrid simulation method for an ultrahigh-voltage DC system with a layered structure, and belongs to the field of simulation and control of a power grid. The electromechanical-electromagnetic transient-state hybrid simulation method is characterized by mainly comprising the following steps of 1, determining a target wire frame of the ultrahigh-voltage DC system with the layered structure; 2, acquiring a running parameter of the ultrahigh-voltage DC system with the layered structure; 3, determining a control system of the ultrahigh-voltage DC system with the layered structure; and 4, performing electromechanical-electromagnetic transient-state hybrid simulation on the ultrahigh-voltage DC system with the layered structure. By the electromechanical-electromagnetic transient-state hybrid simulation method, simulation and analysis on an ultrahigh-voltage direct current accessed to a receiving-end power grid in a layered way can be effectively and reliably performed, and a technological basis and a practical simulation method are provided for effectively mastering running characteristic and an interaction mechanism of the ultrahigh-voltage direct current accessed to the receiving-end power grid in the layered way.