The purpose of this study is to propose the basic data for the development of a sensor capable of simultaneously measuring the liquid-level, concentration and temperature of a urea tank using ultrasonic and electrical conductivity sensors for diesel vehicles with a urea-SCR system. It was found that the liquid-level of the urea tank using the ultrasonic sensor showed a good linearity with the actual liquid-level, and the urea concentration maintained good linearity in the range of 32.5 wt% to 10 wt%. It was an effective measurement of urea temperature to use the electrical conductivity sensor in the temperature range of ？10~22℃ and to use the ultrasonic sensor at 22℃ or more. Simultaneous measurement of concentration, liquid-level and temperature of the urea tank will be possible by attaching the electrical conductivity sensor and the ultrasonic sensor (split-type) to one sensor together.