Abstract: With GM (geometrical midline) yield criterion, the plastic collapse load of defect-free pipe elbow under inner pressure was analyzed and an analytical solution was obtained. The solution showed that the collapse load is a function of wall thickness t, average radius r, yield strength as well as curvature radius R0. The collapse load increases with the increase of the curvature radius R0 and is the same as the burst pressure of straight pipe if R0&rarr∞ is assumed. The plastic collapse load calculated by the solution was compared with those based on Tresca, Mises, as well as TSS yield criteria. Tresca criterion predicts the lower bound of the collapse load, while TSS criterion predicts the upper bound. However, the collapse load on the GM criterion lies just between the TSS and Tresca solutions-most notably, the GM criterion almost has the same precision with the Mises solution.