In this article, the humidity sensors based on the vinylpyridine (VP)-butyl acrylate (BA)-styrene (St) copolymers are developed. The influencing factors of the copolymer＇s humidity sensing properties, such as the mol percentage of the fed monomers and the quaternization reagent ratio (namely, dibromobutane :butyl bromide ratio), are studied, and the long-term stability of the copolymers is investigated as well. The results show that as the content of BA increases and the content of St decreases, the copolymer＇s hysteresis and response time decreases, and with the increasing of the quaternization reagent ratio, the copolymer＇s hysteresis and response time decreases. Also, the sensors based on the copolymers show 2-3% RH reproducibility under various long-term test conditions. These results demonstrate an overall excellent performance in the reproducibility and long-term stability.