Abstract: Based on the principle of minimum potential energy, a general method, called finite member element method, is developed for buckling analysis of thin-walled members with shear lag in the present paper. A linear function is used to express the warping displacements along the cross section of the thin-walled member. The present method is applicable to thin-walled members of any cross section with any boundary conditions. In order to evaluate this method, the critical loads of I-beams subjected to various loading conditions and different boundary conditions are studied. Numerical examples show that the present method is efficient and versatile. It offers more reliable and accurate results as compared to the classical theory of thin-walled members.