The utility model relates to a crane with a horizontal support arm, which comprises a support chassis module, a platform module, a tower body, an electrical control module, the horizontal support arm, a swinging support arm, a lifting arm, a stay cable and a pull rod. The platform module is arranged on a support chassis, the tower body is arranged on the platform, the electrical control module is also arranged on the platform, the horizontal support arm, the swinging support arm and the lifting arm are arranged at the top of the tower body, the stay cable is connected between the platform module and the top of the tower body, and the pull rod is connected with the platform module and one end of the horizontal support arm. The horizontal support arm is a T-shaped structural component with a side horizontal support arm and a rear horizontal support arm, wherein the side horizontal support arm is arranged vertical to a variable amplitude plane, the rear horizontal support arm and the lifting arm are arranged in the same variable amplitude plane, and the end of the rear horizontal support arm is provided with a variable amplitude pulley block. The horizontal support arm is arranged at the top of the tower body through a pin shaft and vertical to the axial line of the tower body, and the end of the horizontal support arm is connected with the platform module through a folding pull rod (or guy rope).