The thermodynamic properties of saturated liquid ammonia were modeled by molecular dynamics simulation. The densities and the specific enthalpies of saturated liquid ammonia are modeled with the site-site potential model. The maximum relative deviations between the simulated results and the database of NIST are less than 1.5% for the density and less than 3.2% for specific enthalphy. The results show that the simulation method is feasible to predict the thermodynamic properties of the single component substance by using the reasonable potential model and parameters.