The　four-mid-node　plane　model　of　base　force　element　method　(BFEM)　on　complementary　energy　principle　is　used　to　analyze　the　rock　mechanics　problems.　The　method　to　simulate　the　crack　propagation　using　the　BFEM　is　proposed.　And　the　calculation　method　of　safety　factor　for　rock　mass　stability　was　presented　for　the　BFEM　on　complementary　energy　principle.　The　numerical　researches　show　that　the　results　of　the　BFEM　are　consistent　with　the　results　of　conventional　quadrilateral　isoparametric　element　and　quadrilateral　reduced　integration　element,　and　the　nonlinear　BFEM　has　some　advantages　in　dealing　crack　propagation　and　calculating　safety　factor　of　stability.