Incompressible flow simulations governed by the two-dimensional Navier-Stokes model are presented in this work. This set of nonlinear equations is approximated by the lattice Boltzmann method (LBM). Numerical method is developed and implemented in both sequential and CUDA programs. The accuracy of numerical scheme is investigated by simulating two-dimensional duct flows that analytical solution exists. CUDA is used to improve computational performance. Speed up is increased approximately 10x from a sequential program.