Underwater excavation prefabricated open caisson bottom center offset measuring method

The invention discloses an underwater excavation prefabricated open caisson bottom center offset measuring method which comprises the steps that 1, a fixed beam (2) is arranged in a blade foot ring (11) of an open caisson (1), and the center of the fixed beam is connected with a floating ball (4) through a hanging rope (3); 2, the floating ball floats on the water surface (5) through the hanging rope; 3, a binocular camera (6) is arranged above the floating ball, two cameras of the binocular camera are symmetrically located on the two sides of the floating ball, a measuring point coordinate model is established, and the coordinates of the center of the floating ball in a camera coordinate system are obtained through the binocular camera and the measuring point coordinate model; 4, calibrating a camera coordinate system, converting the camera coordinate system into a world coordinate system, and obtaining coordinates of the center of the floating ball in the world coordinate system; and 5, comparing the coordi