Abstract: Studied are two commonly used stand locking methods for the lateral roll-changing 3-roll mandrel pipe mill, namely the vertical locking method and the oblique locking method.Analyzed are the influences of these two locking methods on the roll positioning accuracy and their capability of bearing the axial roll forces.Based on the analysis, it is concluded that the vertical locking method has positive influence on the roll positioning accuracy of the 3-roll mandrel pipe mill;and although the oblique locking method decreases the roll positioning accuracy, it can endure bigger axial roll forces and stabilize the positioning of rolling stand, which makes it a more reliable mechanism of stand locking.