The chemical and electrical properties of BDN-SA Langmuir-Blodgett films in air and N2H4 gas respectively, were studied using X-ray Photoelectron Spectroscopy (XPS) and the electrical resistance measurement. The results indicate that the oxidation effect caused by air leads to the lust of N and par tial oxidation of Ni and S in the LB films; while the reduction effect induced by N2H4 eas decreases the amount of O in the LB films. The electrical resistance of LB film decreases dramatically after the film bring exposed to N2H4 gas while increases with the exposure time in air.