In order to measure the motion characteristics of the pointing mirror of the hyperspectral imager, a non-contact measuring system of the pointing mirror is designed. Before processing and aligning, it is extremely necessary to make an error distribution scheme according to the system′s uncertainty which is impacted by various error sources in processing and aligning. The mathematical model with errors of processing and aligning is established via the homogeneous coordinate. The curve of rotation angle and spot position is obtained by curve fitting. The error distribution scheme is determined based on the error of relative position measurement. The error distribution scheme ensures that the measurement uncertainty is 2″ and the resolution is 0.5″ in 11° measurement range. The error distribution scheme reduces the accuracy requirements of processing and aligning and validates the feasibility of the system design.