Abstract: NASICON（sodium super ionic conductor） solid electrolyte was prepared by sol-gel method.The structure of the material were analysized by XRD and mean grain size was 22nm.A toluene gas sensor with well sensing performance was fabricated using NASICON as the Ion conductive layer and samarium oxide as the sensing electrode.The sensitivity of the sensor to（5-50）×10^-6 toluene was-75mV/decade at the operating temperature of 430℃.In addition,the sensor exhibited high selectivity and well response-recovery characteristic to toluene.The response time of the sensor to 5×10^-6 and 50×10^-6 toluene was 45 and 35 s,the recovery time was 8 and 60 s.The sensing mechanism of the sensor was investigated briefly.