Abstract: The boundary element method (BEM) is proposed to analyze the elasto-plastic problems of 2-D orthot ropic st ructures. The boundary integral equation, internal st ress expression, BEM analysis formulae and elastoplastic st ress computation were established, respectively. In the elasto-plastic analysis, Hill-Tsai yielding criterionwas adopted, and the initial st ress method and tangent predictor-radial return algorithm were used to determine thereal st ress state. The elasto-plastic st resses and plastic zones of 2-D orthot ropic st ructures were analyzed with theproposed method, and some numerical result s were compared with the existing ones. Good agreement was observed,which demonst rates the validity of the present BEM in elaso-plastic problems of 2-D orthot ropic st ructures.