Molecular dynamics simulations (MD) are carried out in order to investigate the wettability and pore size dependence of the saturation pressure of the water molecules in nanocylinder and to verify the Kelvin equation. The Kelvin equation quantitatively coincides to the MD results for the nanocylinders with the diameter of 4.2 and 5.2 nm in the case of the intermediate-wetting and hydrophilic nanocylinders. In the case of the hydrophobic nanocylinder, the saturation pressures are at most 10% higher than the estimation of the Kelvin equation with the diameter from 2.2 nm to 5.2 nm.