Abstract: Based on the principle of exergy- economics, an approach of synchronized design for thermal pipeline and its insulation from the point of profit is proposed. An equation for annual net profit of thermal pipeline and its insulation is derived by taking into account the convective heat transfer inside the pipe. By this equation, the effect of pipe diameter and insulation thickness on the annual net profit is analyzed. In addition, to increase the annual net profit of transporting the working media in the thermal pipeline, an equation is proposed to calculate the optimal pipe diameter and insulation thickness.