A　mixed　three-node　triangular　element　with　continuous　nodal　stresses　(mixed　T3-MINI-CNS)　is　presented　for　dynamics　of　porous　media　based　on　the　three-variable　u-w-p　Biot　model　and　the　numerical　manifold　method　(NMM).　The　displacement　and　velocity　approximations　are　derived　using　the　constrained　and　orthonormalized　least-square　(CO-LS)　scheme,　which　possess　continuous　derivatives　and　Delta　property　at　nodes.　The　pressure　approximation　takes　linear　piecewise　interpolation.　Relative　to　higher-order　element,　the　mixed　quadratic　six-node　triangle,　mixed　T3-MINI-CNS　can　model　dynamic　response　of　porous　media　more　precisely　with　fewer　unknowns,　especially　the　short-term　transient　response.　Moreover,　mixed　T3-MINI-CNS　is　immune　from　locking　in　both　undrained　and　rigid　skeleton　limits　and　achieves　more　accurate　pressure　results　than　other　characteristic　locking-free　elements.　Based　on　NMM　and　u-w-p　formulation,　the　most　versatile　three-node　triangular　mesh　can　always　be　used,　avoiding　difficulties　in　mesh　generation.　As　fluid　acceleration　is　involved,　mixed　T3-MINI-CNS　is　capable　of　totally　predicting　dynamic　response　of　porous　mixture,　especially　under　rapid　loading　condition.　In　addition,　reliability　and　precision　of　the　time　integration　are　assessed　in　terms　of　the　energy　balance　condition.　Through　calculating　benchmark　problems,　convergence,　accuracy,　and　reliability　of　the　mixed　T3-MINI-CNS　are　thoroughly　investigated　and　validated.