The invention discloses a high-voltage DC power transmission system equivalent current-and-voltage source modeling method which is suitable for large power-grid electromechanical process simulation. The method comprises the following steps of analyzing a dynamic characteristic of DC voltage and DC current under the same disturbance type, and determining different periods of fluctuation and the characteristic of each period; performing fitting on the current and voltage characteristic of each period by means of a corresponding function, and obtaining a respective segmented function model; performing equivalence on each function section of the current and the voltage by means of a corresponding current source and a voltage source, and switching each segmented function by the current source and the voltage source according to a time sequence. According to different controlled states of a DC system in a fault process, a rectifier station can be simplified to an equivalent current source; an inverter station can be simplified to a voltage source; and an operation characteristic and output power of the whole DC system can be determined by the states of the corresponding current source and the voltage source. The high-voltage DC power transmission system equivalent current-and-voltage source modeling method has advantages of ensuring a main dynamic characteristic of power of the DC system, reducing modeling complexity and difficulty, and reducing calculation amount in simulation.