The invention provides an equivalence method of an electromagnetic transient model of a local power grid suitable for ultrahigh-voltage (UHV) DC access. The problems of large power grid scale, multiple components, lack of electromagnetic transient parameters and low operating efficiency of simulation software during global electromagnetic transient modeling after the access of a UHVDC project intoa power grid are solved. The provided method can be used to accurately and effectively make electromagnetic transient analysis of a UHV power grid containing UHVDC project access. According to the characteristics of voltage distribution under normal operating conditions, the positive sequence equivalent impedance under a three-phase grounding fault and the zero sequence equivalent impedance undera single-phase grounding fault, the errors between the simulation values in a simulation model and the calculated values based on PSASP software are small, that is to say, a constructed UHVDC receiver AC equivalent power grid can satisfy the requirement for power grid transient analysis after the access of a UHVDC project.