The invention provides a triaxial corner fine adjustment mechanism and belongs to a corner fine adjustment mechanism. A worm component in a transition fine adjustment module is mounted on a bracket module; the worm component is connected with the transition fine adjustment module; and a tail end fine adjustment module is mounted on a transition fine adjustment platform. The mechanism has the advantages that the mechanism is novel in structure and overcomes the disadvantage that triaxial corner posture information adjustment cannot be achieved by the traditional uniaxial or biaxial corner fine adjustment mechanism; the inaccuracy of a fine adjustment process caused by axial play arising from a reverse back clearance in a worm-gear transmission process is effectively reduced; the structural stiffness of the tail end fine adjustment module is improved; inaccurate adjustment caused by the reverse back clearance in a helical pair movement process is avoided; and the possibility of damaging the original posture due to secondary force application in a locking process in the traditional fine angle adjustment mechanism is effectively avoided. The mechanism is high in self-locking performance and high in adjustment accuracy, and an adjustment method is easy to realize.