Abstract: A calibration method for deflection angle of mini-type optical seeker is presented. This method firstly obtains the images from the camera in the seeker when the seeker is rotating with its own rotation axis, and then calculates the placement points of central line of sight and the origin of the camera coordinate system in different rotation angles, finally gets the geometric relationship by fitting the distribution of these two groups of points, and then the deflection angle can be calculated. Three sets of experimental data are presented, which give the calibration error of this method, the number of sampling points needed in practice, and the application, respectively. The experimental results show that this method can be used to calibrate the deflection angle of the optical seeker fastly, and the calibration absolute error is less than 0.10 °.