The invention belongs to the field of optical measurement and relates to an optical plumbing compensator. The device consists of an equicrural reflecting prism, an upper planar lens, optical liquid, an inversion prism, a lower planar lens and a shell, wherein the lower planar lens is bonded with the edge of the bottom surface of the equicrural reflecting prism; an air interlayer is reserved at a middle light-permeable position; the upper planar lens and the lower planar lens are parallel to each other; the optical liquid is injected between the upper planar lens and the lower planar lens, and sealed by the shell; and the inversion prism is fixed at an emergent light path. Due to a corresponding relation between refraction and reflection of the optical liquid, the inversion prism and the equicrural reflecting prism, a vertically downward light beam of an object space passes through the device, and an emergent light beam always keeps constant relative to the direction of the upper planar lens and the shell and is independence of a placement attitude of the shell. The optical plumbing compensator can be widely applied to vertically upward automatic compensation for target parallel light tubes, charge coupled device (CCD) cameras and laser optical plummets.