The bridge crane system has been widely used in industrial production. This mechanical system is a typical underactuated system that has one control input and two degrees of freedom (DOF). This paper discusses the stabilizing control problem for this 2-DOF underactuated mechanical system. A fixed-time hierarchical sliding mode control method is developed. The method firstly constructs two first-level sliding surfaces and a second-level sliding surface for the bridge crane system. Then, a sliding mode controller is designed to stabilize the second-level sliding surface at the origin within a fixed time. It guarantees the fixed-time convergence of two first-level sliding surfaces at the origin. This further ensures the system’s fixed-time stabilizing control objective to be achieved. Numerical simulation experiment results verify the effectiveness of the presented method.