In　this　paper,　we　present　the　Euler　implicit/explicit　scheme　for　the　three　dimensional　nonstationary　Navier-Stokes　equations.　The　Galerkin　mixed　finite　element　satisfying　inf-sup　condition　is　used　for　the　spatial　dis-cretization　and　the　temporal　treatment　is　implicit/explict　scheme,　which　is　Euler　implicit　scheme　for　the　linear　terms　and　explicit　scheme　for　the　nonlinear　term.　We　prove　that　this　method　is　almost　unconditionally　convergent　and　obtain　the　optimal　H-1　-　L-2　error　estimate　of　the　numerical　velocity-pressure　under　the　hypothesis　of　H-2　-　regularity　of　the　solution　for　the　three　dimensional　nonstationary　Navier-Stokes　equations.　Finally　some　numerical　experiments　are　carried　out　to　demonstrate　the　effectiveness　of　the　method.