Prepared by a sol-gel process, the lead zirconate titanate (PZT) (PbZr 0.3 Ti 0.7 O 3 ) thin film, which is chosen as an infrared sensing film, uses lead acetate trihydrate, zirconium acetylacetone, acetylacetone, and titanium isopropoxide as starting materials. The pyroelectric infrared sensor with the PZT thin film has been successfully fabricated. The fabrication process of the device is discussed in detail. A new Au Pt-PZT-Pt infrared detecting structure on silicon substrate with a micro bridge is designed. Under the response and reference dual-element configuration, undesirable signals, caused by vibration, ambient temperature change, and sunlight, are cancelled out at the input of the preamplifier circuit. The dual-element structural design of the device is discussed and analyzed in detail. In order to realize our purpose to use this detector to monitor gas concentration, we designed a detection set-up in the light of a certain gas which absorbs infrared radiation at specific wavelengths. The gas concentration is obtained by designing a weak signal detect circuit and data arithmetic. The first measurement for methane is reported. Experimental result shows the ability of methane detection of the detector based on the infrared sensor element.