The invention discloses a differential marine cycloidal propelling device. A prime motor drives a main shaft; the main shaft is rotatably matched with a base; the base is provided with a hollow rotating disc; the top surface of the rotating disc is fixedly connected with the main shaft; a rudder shaft passes through the main shaft; the upper end of the rudder shaft is fixedly connected with a steering engine, and the lower end of the rudder shaft passes through the rotating disc and a central gear positioned in the rotating disc and is rotatably matched with the bottom surface of the rotatingdisc; the rudder shaft is movably matched with the top surface of the rotating disc and is fixedly connected with the central gear; a plurality of paddle rotating shafts are rotatably matched in the rotating disc, are parallel to the main shaft, are arranged along the circumferential direction by taking the central gear as a center, and traverse and are fixedly connected with a paddle gear; the paddle gear is linked with the central gear through a transmission piece; one end of each paddle rotating shaft is fixedly connected with a paddle positioned outside the rotating disc respectively; andthe rotating disc rotates a circle, and the paddle rotates a semi-circle around the axis of the paddle. The differential marine cycloidal propelling device has the advantages of integrated rudders and paddles, high hydrodynamic efficiency, low energy consumption and the like, and is stably operated.