Abstract: A finite strip method is first set up for the large deflection elastoplastic analysis of initially imperfect thin retangular plates subjected to in—plane loads. The ultmate loads of the plates are calculated using a area approach associating a modified Ilyushin or Ivanov yield criterion and the prandtl—Reuss flow rules. Comparison of analytic results obtained by the finite strip method with available theoretical results is very good agreement, which reveals that the finite strip method is extremely accurate in large deflection elastoplastic analysis.