Accurate measurement of three-dimensional attitude angle is widely used in aviation, aerospace, national defense and other fields. In order to realize convenient and accurate measurement of three-dimensional attitude angle, an optical system based on a lens array is designed and an analysis model of micro-three-dimensional attitude angle measurement is established in this paper. In the system, the collimated parallel beam passes through four array lenses arranged in a pyramid shape to form regular array spots on a CCD. By analyzing the distance between the spots on the CCD image, the distance between the adjacent aperture on the lens array and the inclination angle between the lens array and CCD, the beam pitch angle and azimuth angle relative to the receiving system can be obtained. By using the angle of the lines of the array spots relative to the horizontal or vertical plane, the roll angle about the Z axis can also be obtained. Compared with the measurement results of the high-precision autocollimator, the measurement accuracy of the proposed method is verified to be RMS≤0.1″. The results show that the proposed method can realize the measurement of three-dimensional attitude angle.