A novel ethanol sensor based on RuO 2 -modified Ni as working electrode in alkaline solution was developed. The sensing results were affected by the RuCl 3 concentration, thermal decomposition numbers and ultrasonic irradiation for preparing the working electrode. The results showed that the ethanol oxidation was more efficient at the RuO 2 -Ni electrode than at bare nickel electrode. The optimal operating conditions of the RuO 2 -modified Ni electrode were 2M Ru 3 + , six times of repeat thermal decomposition numbers and 150W of ultrasonic irradiation. The results also indicated that response time of the prepared ethanol sensor is 13s and the best sensitivity is 4.92μAppm - 1 cm - 2 .