This paper presents a novel scheme to incorporate quantum effect in classical hydrodynamic model. The scheme can be applied to multi-dimensional and transient conditions and no additional equations are required to solve quantum potential, so complexity of equations is drastically reduced. Simulation results show consistent with that of Monte Carlo simulation. This technology provides an efficient method for investigating quantum effect in small size semiconductor devices. A new guess method for hydrodynamics model has also been proposed in this paper and a 2D hydrodynamic simulator based on quantum correction and new initial guess method has been developed. The solution obtained from DD model gives a good initial guess of HD model. Its advantage is it can achieve convergence after a few iterations because initial guess is closed to final solution. Two-dimensional simulations have been carried out on a few nanoscale devices. The results have been compared with that of other initial guess methods and the significant differences have been found, especially in numerical stability.