ADI method is often used to calculate imcompressible Navier-Stokes equations^[1]. In the ordinary ADI method, the nonlinear con-vective terms and noslip condition are delayed and streamfunction-vorticity Navier-Stokes equations are uncoupled. So it can't keep comlete two-order accuracy and complete implicit. In this paper, a "alternating linearize" technique for the nonlinear terms is presented, so streamfunction-vorticity Navier-Stokes equations can be coupled and boundary points and inner points are simultaneously solving.This method seems to keep complete two-order accuracy. It is utilized to calculate the "two-dimensional cavity" flow problem at Reynolds number 1, 10, 100, 500, 1000 and 2000. The result shows that the improved ADI scheme has the advantage of unimproved one.