Abstract: PANI-TiO₂ composites were prepared by sol-gel method and in situ polymerization. The gas sensing properties of PANI-TiO₂ composite films were characterized by Keithley236. The results show that the film has a good response to trimethylamine at room temperature, the sensitivity can be changed by 3~4 orders of magnitudes in about 3 minutes. The film has good selectivity for similar gases, and can be completely recovered by high purity nitrogen at room temperature.