The invention discloses a lifting hydraulic device for a car ferry gangplank, and relates to the technical field of hydraulic control. The lifting hydraulic device comprises two oil pump motor groups, wherein the oil pump motor groups are communicated with plunger cylinders arranged on a port and a starboard of a bow and on a port and a starboard of a stern via oil tubes through balance valve groups. The plunger cylinders are fixed on the side walls of a ferry body, both ends of each plunger cylinder are connected with pulley blocks, and wire ropes wound on the pulley blocks are connected with the car ferry gangplank through guide pulleys. Travel switches are arranged on guide rails arranged in front of the pulley blocks in the moving direction of the pulley blocks, and emergency descending switches are arranged in loops of the balance valve groups. The lifting hydraulic device can solve the problems that the car ferry gangplank only has a few lifting speed adjusting gears, the lifting speed cannot be continuously adjusted, the equipment maintenance is inconvenient, and the use efficiency is low.