A computer vision method based on image motion blur is proposed for the measurement of angular velocity in this paper. Motion-blur may hide vital motion information, which has been almost ignored in conventional methods for motion perception. In order to reveal the relationship between rotation and image blur, the fundament trade off between motion-blur in spatial and frequency domain has been exploited to obtain motion information. There is a series of dark parallel lines on the spectrum of the translation-blur image, which are related to the displacement of translation during the exposure time. The polar transformation has been applied to the rotation-blur image to reduce the rotation to translation. Therefore, these dark lines are exactly related to the angular velocity of rotation. The information of these lines has been extracted by some image processing techniques, and then the angular velocity can be obtained. The proposed computer vision method is applied to estimate the angular displacement of simulated images and the rotary speed of actual images. The results of simulation proved that this method is applicable for measuring. And then experimental results showed that the method based on the computer vision is feasible.