Abstract: The structure, composition, crystal phase and conductivity of YSZ thin films, deposited on NASICON （Na⁺ Super Ionic Conductor） substrates by RF magnetron sputtering, were studied. The results showed that the YSZ films were condensed, crack-freeand transparent. The conductivity of the films is slightly higher than that of the sintering YSZ bulk. The NO₂ sensors constructed by YSZ|NASICON|Ba(NO₃)₂ showed that its response time is about 3 min and it can detect NO₂ gas at 10 ppm magnitude.