The invention discloses a spreader stabilizing mechanism of a container
gantry crane, comprising a drum group, a
pulley block, a spreader upper frame and a steel
wire rope group wound on the drum group and the
pulley block; the steel
wire rope forms four congruent inverse triangles at the space between the spreader upper frame and a
pulley frame; the bottom points of the four inverse triangles are distributed at the four corners of the spreader upper frame symmetrically; included angles which are formed by the planes of the four inverse triangles and the moving direction of a
cart and a trolley are all acute angles. Therefore, in the moving direction of the
cart and the trolley, the motion damping of the four space triangles exists, thus reducing the swing of the spreader; when the load of the spreader is not balance and the swing of opposite angles is generated, namely, twisting and vibration are generated, the space triangle forms the motion damping in the
diagonal direction of the upper surface of the spreader upper frame and forms damping component in three directions of the space, thus offsetting the swing of the opposite angles. The invention has simple structure, convenient maintenance and use and high safe reliability.