The invention discloses a mechanical device used for preventing sinking of a passenger ship in an inland river. The mechanical device comprises a dual hydraulic cylinder transmission device and an integrated detecting and releasing device, in the integrated detecting and releasing device, data detected by a posture sensor and a water pressure sensor is input into an automatic controlling system, and the automatic controlling system conducts processing on the data and controls the dual hydraulic cylinder transmission device and a valve of an airbag. The dual hydraulic cylinder transmission device comprises a hydraulic cylinder A and a hydraulic cylinder B, the hydraulic cylinder A and the hydraulic cylinder B are connected to a hull through mounting parts, and the mounting parts are each ina long strip shape and are fixed on the side face of the hull; and the tail end of a cylinder body A is hinged to one ends of the mounting parts, the tail end of the cylinder B is hinged to the otherends of the mounting parts, and the front end of a piston rod A is hinged to a cylinder body B. According to the mechanical device used for preventing sinking of the passenger ship in the inland river, not only can restoring torque of the hull of the big passenger ship during transverse overturning be increased, but also the effect of preventing the hull from overturning can be achieved through judging the transverse overturning state of the hull of the big passenger ship in the inland river.