Optical pressure sensor plays a very important role in micro deformation detection, environmental monitoring, and medical fields. However, the quantitative relationship between the applied pressure and the optical response of the resonator before and after deformation is difficult to obtain. In this paper, a coupled resonator system based on metal-insulator-metal waveguide for optical pressure sensor is proposed. The mechanical properties of the system and the optical transmission properties before and after applied pressure are analyzed in detail by using the finite element method. Simulation results show that the maximum deformation of the resonator has a simple linear relationship with the applied pressure. We give a direct definition of the sensitivity of the optical pressure sensor. And based on the Fano resonance phenomenon caused by the coupling the slot cavity with the groove cavity, the optical pressure sensor with a sensitivity of 6.75 nm/MPa is achieved. In addition, we add stub resonator to obtain double Fano resonance phenomenon, and with the change of external pressure, the two Fano line types show different change laws. Specifically, a suitable pressure value can make a double Fano resonance become a single Fano resonance. The special features of our suggested structure are applicable to detecting optical property changes under different pressures, chemical high pressure experimental measurement and study of chemical reaction kinetics process.