A study of plastic buckling of a circular cylindrical shell subject to axial, torsional and circumferential loading stresses is presented. In the deformation model, the transverse shear is taken into account by a first-order theory with a correction factor. For the buckled equilibrium, the contributions of both v (circumferential displacement) and w (normal displacement) to the buckling are included so that a better accuracy can be achieved. J2 deformation theory and J2 flow theory of plasticity are used for the establishment of the constitutive relations for buckling analysis. With the existence of torsional load, the equation of radial equilibrium includes the term of mixed second-order derivative ∂2w/∂x ∂y and the plastic in-plane stress–strain relations are anisotropic, and therefore a handy form of solution in terms of trigonometric functions is no longer possible. Consequently, the finite difference method is used. To improve the accuracy, a five-point finite difference scheme is employed instead of the conventional central difference. Numerical results of examples show the interactive roles of the in-plane loads in the plastic buckling.