A marine lifeboat comprises a roller, a first motor, a first strut, a rope, a rack, a first sliding block, a first sliding rail, an upper plate, a first gear, a third strut, a lower plate, a controller, first cylinders, a second strut, a second motor, a second gear, a first connecting rod, a second cylinder, a second connecting rod, a third connecting rod, a third cylinder, a second sliding rail, a fourth connecting rod, a sliding plate, an engine base, a fourth cylinder, a second sliding block, a second electromagnet, an elastic strap, a first electromagnet, a lifeboat, a fifth cylinder, a sixth cylinder and a supporting rod. Two first cylinders are installed on the lower plate, the upper plate is installed on the first cylinders, the first sliding rail is installed on the upper plate, the first sliding block is installed on the first sliding rail, the supporting rod is installed on the first sliding block, the rack is installed on the right side of the supporting rod, and the first gear is installed on the lower portion of the rack. The marine lifeboat has the advantage that the lifeboat can be placed in the sea automatically.