In　this　paper,　we　study　the　stability　and　convergence　of　the　Crank-Nicolson/Adams　Bashforth　scheme　for　the　two-dimensional　nonstationary　Navier-Stokes　equations.　A　finite　element　method　is　applied　for　the　spatial　approximation　of　the　velocity　and　pressure.　The　time　discretization　is　based　on　the　Crank-Nicolson　scheme　for　the　linear　term　and　the　explicit　Adams-Bashforth　scheme　for　the　nonlinear　term.　Moreover,　we　present　optimal　error　estimates　and　prove　that　the　scheme　is　almost　unconditionally　stable　and　convergent,　i.e.,　stable　and　convergent　when　the　time　step　is　less　than　or　equal　to　a　constant.