We have studied numerically the dynamics of the microphase separation of a water-oil-surfactant system. We developed an efficient and accurate numerical method for solving the two-dimensional time-dependent Ginzburg-Landau model with two order parameters. The numerical method is based on a conservative, second-order accurate, and implicit finite-difference scheme. The nonlinear discrete equations were solved by using a nonlinear multigrid method. There is, at most, a first-order time step constraint for stability. We demonstrated numerically the convergence of our scheme and presented simulations of phase separation to show the efficiency and accuracy of the new algorithm. (c) 2006 Elsevier Inc. All rights reserved.