We　propose　an　efficient　scheme　for　realizing　two-mode　squeezing　for　two　cavity　modes　with　an　atomic　ensemble　trapped　in　the　cavity　and　driven　by　two　classical　fields.　Through　a　suitable　choice　of　the　driving　classical　fields,　the　evolution　dynamics　of　the　two　cavity　modes　is　decoupled　with　the　atomic　system　and　described　by　a　two-mode　squeezing　operator.　We　show　that　a　highly　squeezed　state　can　be　obtained　at　the　output　even　with　a　bad　cavity.　The　required　experimental　techniques　are　within　the　scope　of　what　can　be　obtained　in　the　BEC-cavity　setup.　©　2014　Chinese　Physical　Society　and　IOP　Publishing　Ltd.