This paper investigates how non-perpendicularity in a tri-axial velocity sensor would affect the tri-axial velocity-sensor#39s azimuth-elevation beam-pattern in terms of the beam#39s pointing direction and directivity. The vertical axis was adopted as the reference axis for the analysis and a rotation matrix developed to represent the non-perpendicularity in Euclidean space. The beampattern of this deformed tri-axial velocity sensor is then analytically studied. It was found that the non-perpendicularity does not affect the overall shape of the beampattern, but only introduces a pointing offset. Also, the non-perpendicularity imperfectionreduces the directivity of the imperfect triaxial velocity sensor relative to a perfect case. This finding developed in closed the pointing bias for the described deformity hence serves for non-iterative post data acquisition correction.