In　order　to　study　the　influence　of　stiffness　on　the　mechanism　of　failure　and　ultimate　bearing　capacity　of　weightless　and　homogeneous　subsoil.　Mohr-Coulomb　inscribed　circle　yield　criterion　and　associated　flow　rule　are　adopted.　The　overall　process　of　subsoil　from　elasticity　to　plasticity　gradually　is　modeled　by　elastoplastic　FEM　through　load　increment　method.　Computed　results　of　three　sort　of　foundation　mentioned　above　are　compared　and　integrated　with　some　important　results　of　model　test,　some　significant　conclusions　can　be　obtained.　The　relativly　accurate　subsoil　bearing　capacity　of　stripe　shallow　foundation　can　be　calculated　by　adopting　Mohr-Coulomb　inscribed　circle　yield　criterion　and　associated　flow　rule.　The　difference　of　Nc　between　flexible　foundation　model　and　rigid　foundation　model　increases　with　the　angle　of　frictional　resistance　accretion.　Both　the　location　and　the　character　of　the　first　crack　are　qiute　different.