With the rapid development of surface mount technology， higher requirements are put forward for mark positioning technology based on machine vision. In this paper， a fast and high accuracy positioning algorithm for triangular ring mark is proposed. By using geometric features of convex hull and constructing the concept of deviation histogram， the negative factors which affect the positioning accuracy are eliminated from coarse to fine， such as arc corners， convex points， subtle bumps and burrs. Then， a high-quality data set for fitting sides of triangle ring is obtained. Finally， the fitted equations of each side of the mark are obtained through the linear fitting with the constraint of minimum distance， and the geometric center of the triangle ring mark is calculated to realize the high accuracy positioning. The proposed algorithm provides a state-of-the-art idea for linear marks positioning with high accuracy and fast speed requirement.