Finite　element　method　with　reduced　shear　strength　(SSRFEM)　was　used　to　evaluated　the　base　stability　of　excavations　in　soft　clays　under　the　undrained　condition.　The　influence　of　clay　undrained　shear　strength,　conditions　of　pit　bracing　system　and　pit　dimensions　on　base　upheave　stability　of　excavations　were　studied　detailedly.　The　results　from　several　limit　equilibrium　analysis　methods　for　evaluating　base　stability　of　excavations　were　compared　with　the　results　from　FEM.　It　shows　SSRFEM　is　a　reliable　and　robust　method　for　assessing　the　safety　factor　of　the　base　stability　of　excavations　and　limit　equilibrium　analysis　methods　only　can　be　used　on　some　conditions.