The invention discloses a DC stator excitation type mechanical-electro-liquid coupler which includes a supporting system, a mechanical energy conversion system, a hydraulic energy conversion system, and an electric energy conversion system. The supporting system includes a shell and a distribution plate. The hydraulic energy conversion system includes a cylinder body, a swash plate, a plunger andthe like. The electric energy conversion system includes a rotor coil, a stator iron core, an excitation winding, a lead terminal and the like. The stator iron core and the excitation winding are fixed in the shell, a transmission shaft and the cylinder body are connected by a spline and rotate synchronously, and the plunger reciprocates along the axis to absorb or output the hydraulic oil under the action of the swash plate. In specific work, the lead terminal is externally connected with the direct current, thereby achieving mutual conversion of mechanical energy, hydraulic energy and electric energy. The DC stator excitation type mechanical-electro-liquid coupler has the advantages of compact structure, high conversion efficiency and small pressure loss, achieves the coupling of mechanical-electro-liquid and the conversion of corresponding energy, and has broad application demands and industrialization prospect.