【正】 -The contributions of vacuum fluctuations to energy density in a weak momen-tum dependence of self-energy are calculated in Walecka model.After adjusting modelparameters and introducing momentum dependent form factors at meson-nucleonvertices to reproduce the empirical nuclear matter saturation properties,Hartree-Fockresults including vacuum effects at low to moderate densities are similar to those in therelativistic Hartree approximation.