<p>As carbon neutrality is emphasized in the transportation sector, research on using natural gas, a low-carbon fuel, or hydrogen/ammonia, a non-carbon fuel, as fuel in place of conventional gasoline and diesel fuels is in the spotlight. For gas fuels, it is necessary to accurately and safely measure the amount of remaining fuel in the tank. In this study, the ultrasonic energy propagation characteristics according to the angle were identified by varying the thickness and composition of the matching layer, and the effects of temperature and pressure conditions inside the tank were also analyzed. Experimental results show that the directivity of ultrasonic signals varied depending on the sensor configuration, with most of the signals being reflected from the reflector within the range of ±15° angles. As the ambient temperature around the tank decreased, the sensitivity of the ultrasonic sensor increased and the maximum sensitivity range tended to move backward, and as the pressure inside the tank decreased, the sensitivity of the ultrasonic sensor decreased and the phase tended to lag behind.</p>