An analytical elasto-plastic stress analysis is carried out on thermoplastic composite beams supported from two ends under transverse linearly distributed load. The composite beams consist of woven steel fiber and thermoplastic matrix. The material is assumed to be perfectly plastic for the elasto-plastic solution. The expansion of the plastic,region and the residual stress component of sigma(x) are determined for 0degrees, 15degrees, 30degrees and 45degrees orientation angles. The yielding begins at the upper and lower surfaces of the beam at the same distances from the ends. The intensity of residual stress component of sigma(x) is maximum at the upper and lower surfaces but residual stress component of tau(xy) is maximum on the x axis of the beam. The strength of the beam is increased by residual stresses.