Based on conventional metal-oxide-semiconductor field-effect transistor (MOSFET), a novel kind of chemical field-effect transistor (ChemFET) gas sensor array has been designed and fabricated. The obtained sensor consists of self-assembly polyaniline (PAhD composite film containing poly (acrylic acid) (PAA) which was used as gate material of MOSFET instead of conventional metallic gate. The UV-Vis absorption spectra of PAN/PAA films were characterized. The N02 gas sensitive property of the ChemFET sensor array was also Based on conventional metal-oxide semiconductor field-effect transistor (MOSFET), a novel kind of chemical field-effect transistor (ChemFET) gas sensor array has been designed and fabricated. The obtained sensor consists of self-assembly polyaniline (PAhD composite film containing poly (acrylic acid) (PAA) which was used as gate material of MOSFET instead of conventional metallic gate. The UV-Vis absorption spectra of PAN/PAA films were characterized. The N02 gas sensitive property of the ChemFET sensor array was also investigated. Results show that the drain current of devices increases with increasing of back-side voltage, and decreases with the increase of N02 concentration when the N02 concentration is below 20mg/g. The temperature dependence of ChemFET sensor array shows that the drain current of ChemFET sensor decreases with increasing of temperature.