Abstract: A lock device for a garbage compactor of a garbage truck has two cylinders, two connecting bars, two linkages and two hooks. The cylinders are mounted on opposite sides of the garbage compactor. Each connecting bar is connected to one end of a piston rod extending from the cylinder. Each linkage is connected to the other end of the corresponding connecting bar. A hook is pivotally connecting to the linkage and pivotally mounted on the garbage compactor. The hook has a downward engaging portion to engage a post on the garbage compartment. Accordingly, the hooks will not disengage from the posts when a shock occurs. In addition, since a cylinder is used on each side of the trash compactor, the peak load on each cylinder can be reduced, and the useful life of each cylinder is prolonged.