The urea system is used for reducing the NOx emission in the diesel engines. The NOx reduction efficiency is influenced by the urea temperature. Therefore, the urea cooling and heating system is applied in the urea supply system. And the coolant of vehicle is used for the heat source. This study has predicted urea temperature distributions of the urea supply line that is heated by the vehicle coolant. The urea supply line is composed the double wall structure to heat exchange from vehicle coolant to urea. The vehicle coolant temperature is 80℃ and the urea inlet temperature is 60℃. This study performed the numerical analysis using ANSYS CFX v.16 to predict the urea outlet temperature. The urea outlet temperature rise very little due to the urea tube material which is very low conductivity.