Upwind flux vector splitting is presented for hydrodynamic modeling of 1D and 2D deep-submicron semiconductor devices. This approach splits the Jacobian matrices of the hydrodynamic system into two parts corresponding to forward and backward running fluxes, and an upwind difference is applied to each split flux. Influences of the boundary discontinuity of electric field and velocity on transport results in the 2D deep-submicron devices are discussed. The study demonstrates that the developed method is capable of handling large discontinuity of the boundary conditions, and highly non-linear source terms in short-channel semiconductor devices.