Abstract: In order to measure the degree of square of cigarette packet accurately, a method based on computer vision was proposed. The method includes the following steps:first, determine the geometric parameters between components in the measurement device, camera parameters and the lens distortion correction coefficient; second, obtain raster lines image via image processing algorithm, absolute phase values via phase-shift method and multi-frequency heterodyne principle, and 3D coordinate data of each pixel point on packet surface via the relationship between height and phase; finally, acquire the 3D information of the packet from 4 different angles via turning the packet, then establish the cloud of points and calculate the degree of square of the packet. The results showed that the error of angle measurement was lower than 0.2°, and the standard deviation of repeated measurement for degree of square was 0.01, test time less than 3 seconds. This method features good stability and measurement precision, it provides a technical means for avoiding the deformation of cigarette packet in the process in contact measurement.