Abstract: The paper aims to propose a method for modeling the electromechanical transient process of line commutated converter-voltage source converter（LCC-VSC） hybrid DC grid to be used for bulk power system transient stability analysis. Firstly, the basic structure of hybrid DC grid was constructed according to the different technology characteristics of LCC and VSC converters. Then, after analyzing electromechanical transient simulation features and performing rational simplification, the methods for modeling the electromechanical processes of LCC, VSC and DC/DC converter were proposed. Based on Dommel theory, the method for finding the electromechanical transient solution of DC grid was also presented. The modularization design of all elements are realized at PSASP, allowing users to freely build simulation cases. Finally, in view of the conception that renewable generation and conventional generation in energy bases were collected by VSC-HVDC and transmitted by long distance LCC-HVDC to load centers, a four-terminal hybrid DC grid simulation case was designed. The operation characteristics under three different operational modes were compared and analyzed. The simulation results show that the proposed LCC-VSC hybrid DC grid electromechanical transient model is accurate and reliable, which can be applied into bulk power system transient stability study.