Nonresonant photoacoustic gas detection system shows good expectation because of its simple structure, low cost and high sensitivity. A photoacoustic detector based on piezoelectric polyvinylidenefluoride (PVDF) diaphragm was proposed. The properties of PVDF diaphragm was analyzed with finite element approach using ANSYS. A doublelayer structured micropressure sensor based on two pieces of PVDF diaphragms with opposite polarization orientations was designed and fabricated, and the size of the PVDF diaphragms is 10 mm×5 mm×20 μm. The photoacoustic chamber consisting of an absorption chamber and a compensation chamber was designed and the encapsulation of the detector was completed. The CO2 gas sensing properties of the detector were investigated. The relationship between the response of the detector and the concentration of CO2 shows good linearity and the theoretical detection limit of CO2 is about 29×10-6.