The thin film of PbTiO3 is fabricated at substrate temperature of 100-150$^{circ}C$. The infrared spectrum of the ferroelectric thin film is measured as temperature of thermal treatment, 400 - 550$^{circ}C$. According to infrared spectrum analysis, there are absorption bands at a nearby wave number of 1000 $sim$ 400 cm-l and the thin film treated by temperature of 550$^{circ}C$ has absorption bands of wave number 500 cm-l similar to infrared response property of PbTiO3 powder. The pyroelectric infrared detector is fabricated after deposition of Pt and PbTiO3 thin film on Si wafer by sputtering machine. The measured remnant polarization are 11.5-12.5$muC/cm2$, breakdown electric field Ec is 100-120KV/cm, and voltage responsivity and detectivity is -280V/W, -108cm Hz/W.