Polyvinylidene fluoride (PVDF) is used as the sensitive element of pressure sensor, and a pressure sensor used in large area is designed. By calculating the piezoelectric equation of piezoelectric materials, the relationship between pressure input and voltage output is obtained theoretically. By changing the substrate material and substrate thickness of the sensor in ANSYS, the influence of different material and thickness on sensor sensitivity is analyzed by control variable method. The analysis results show that the thinner the thickness of the upper and lower substrate, the closer the simulation voltage value is to the theoretical value; the smaller the elastic modulus of the upper and lower substrate is, the closer the simulation voltage value is to the theoretical value. According to the practical application, we can design the PVDF pressure sensor with PDMS and thickness of 0.05mm.