Thermal conductivities of bulk silicon are calculated by equilibrium molecular dynamics (MD) simulations. Applying common used quantum corrections to the MD results, does not bring them into better agreement with the theoretical predictions or experimental data, while the uncorrected values are closer to the theoretical predictions and experiments below 400K. By assessing the validity of quantum corrections according to theoretical calculations and MD simulations, we demonstrate that the hypothesis of equating the heat fluxes is not reliable. In addition, we explore that the rations of thermal conductivities of MD simulations and quantum calculations are approximate to 1. Then a modified quantum correction for mapping MD simulations to quantum systems is proposed.