Influence of residual stresses (e. g. welding residual stresses) on the instability problem, especially instability of columns with welding residual stresses has been studied for years by many researchers. Howerer, there are few papers on the instability of plate with residual stresses. One of the authors presented a paper on this problem and solved theoretically the influence of residual stresses on the elastic buckling of plates. This report as a continuation of the previous one, treats the plate instability in plastic range of stress as well as in elastic range by using both energy method to determine the critical loads of axially compressed plates and deformation theory of stress-strain relationship in plastic range, and clarified the influence of residual stresses on the strength of compressed plates. Experiments were carried out on the following three series of specimens (supported along all edges and the dimensions of 1200 × 580 × 814 mm), i. e. V -series (no residual stresses), E -series (welded along longitudinal edges) and C -series (welded along centre line), and the test results show a good agreement with theoretical calculation. Conclusively it may, theoretically and experimentally, be said that in case of the plate instability, compressive residual stresses locatad far from supported edges or at loops of the deformed shape of plate, considerably reduce the strength of plate in both elastic and plastic range, while tensile residual stresses in the loops increase the buckling load of plate in elastic range but may decrease the strength of plate in plastic range.