[en] An electrostatic trap for polar molecules is proposed. Loading and trapping of polar molecules can be realized by applying different voltages to the two electrodes of the trap. For ND_3 molecular beams centered at ∼10 m/s, a high loading efficiency of ∼67% can be obtained, as confirmed by our Monte Carlo simulations. The volume of our trap is as large as ∼3.6 cm"3, suitable for study of the adiabatic cooling of trapped molecules. Our simulations indicate that trapped ND_3 molecules can be cooled from ∼23.3 mK to 1.47 mK by reducing the trapping voltages on the electrodes from 50.0 kV to 1.00 kV. (paper)