We propose a novel hydrostatic pressure sensor based on a dual-core photonic crystal fiber (DC-PCF). Two solid fiber cores separated by an air hole in the cross-section lead to two independent waveguides inside the DC-PCF which accompany with mode coupling. The mode coupling of two solid fiber cores of the DC-PCF under different hydrostatic pressure is numerically investigated. A pressure sensing system is proposed and performances of the pressure sensor have been numerically investigated. Our calculations show a hydrostatic pressure sensor based on a 10-cm DC-PCF has a sensing range from 0 to 1000 MPa and a sensitivity of 3.47 pm/MPa.