This study is intended to secure seolge and structural strength of the suspension as necessary amphibious boat amphibious facilitate a possible amphibious boat 7m parenting class. Developed a technique for mounting a three-wheel drive track traveling device to medium-sized vessels, and the control device in order to improve the efficiency of the safety and operation of this device, the braking device of the land driving, the steering apparatus and the linear adapted to install the device development and installation of the wheels on the bottom, leaving space travel wheel award during lift pockets (wheel pocket) analyzed the impact of the ship resistance and stability, and tried to improve the problem.