The invention provides a mechanical adsorbing device for improving ship abreast supply stability. The mechanical adsorbing device for improving the ship abreast supply stability mainly comprises vacuum suckers (1), a hydraulic buffering mechanism (2) and a mechanical arm (3), wherein during working, the mechanical adsorbing device provides restraining forces, buffering forces and pushing forces for two ships at supplying work and can exert the abreast supply process of the two ships to be smoothly finished. According to the invention, by using the double-face suckers to adsorb and fix ship bodies, the supply is stable; due to adoption of the hydraulic buffering mechanism between the suckers, the ship abreast buffering and pushing forces can be provided so that the ship abreast supply stability and safety are improved; and through adoption of a folding type mechanical arm design, the device is easy to mount and operate and deck spaces are saved.