Abstract: Based on the fully discrete scheme proposed by Delfour-Fortin-Payre, This paper is concerned with the Crank-Nicolson finite difference scheme for the non-conservative nonlinear Schrödinger equation (NCNLS). The scheme is second oder accurate in time and space, and we prove that their extensions satisfy discrete versions of the mass and energy balance laws for the NCNLS. An optimal error estimate of the finite difference method in H¹ norm is established without any constraints of the grid ratios. Besides the standard energy method, a 'cut-off' function technique and a 'lifting' technique are introduced in analyzing the proposed scheme. The analytical method presented in this paper can be applied to many other finite difference schemes for solving nonlinear Schrödinger type equations.