Abstract: In this paper the stability problem of composite shell structures, such as single-ply shell, laminated shell and sandwich shell, is solved by displacement mode of finite element method. To suit different geometric shape and variable shell thickness. We select a Mindlin 8-node isoparametric quadratic shell element taking the coupling phenomenon between bending and inplane stretching and the effect of shear deformation into account. The external loads may be distributed aerodynamic pressure, body force or the so-called"heat load"created by temperature difference between external and internal plys. A generalized eigenvalue problem is solved by simultaneous iteration algorithm to find the eigenvalue, which is the smallest in terms of norm, and the corresponding eigenvector. A computer program has been written in standard FORTRAN-IV language. It possesses the advantages of less C. P. U. time, good versatility and convenience for use. Several examples have been tested by the use of the program, computational results are fairly satisfactory. Now this program has been used to check stability of practical composite shells and help engineer design shell structures.