The invention relates to an electromechanical transient modeling method and an electromechanical transient model of a wind turbine generator system, in particular to an electromechanical transient modeling method and an electromechanical transient model of a direct-drive-type wind turbine generator system. The modeling method includes the following steps: firstly, a generator-side model of the wind turbine generator system is constructed. Secondly, a direct current and unloading circuit model of the wind turbine generator system is constructed. Thirdly, a grid-side converter and control system model of the wind turbine generator system is constructed. And lastly, a low voltage ride through control model of the wind turbine generator system is constructed. Based on a practical physical device, by means of a reasonable presume, an electromagnetic transient model of the direct-drive-type wind turbine generator system is simplified, and meanwhile, the dynamic process of direct current voltage and low voltage ride through characteristics of the converter are taken into account. The simulation result shows that the simulation curve of the model is consistent with practically detected low voltage ride through curve of the direct-drive-type wind turbine generator system, and the result is accurate and reliable. The electromechanical transient modeling method and the electromechanical transient model of the direct-drive-type wind turbine generator system are used for analyzing influence on transient stability of a power system when a large-size direct-drive-type wind power plant is introduced.