Abstract: The compact transmission line is a new tendency of the development of power transmission.Based on the electrical theory,this paper introduces the principle of improving the transmission capacity with the compact line of large surge-impedance loading power.The mathematical model of the conductor capacitance is also discussed.By means of raising the capacitance to the ground of the conductors and reducing the wave impedance of the conductors,the basic theory for raising transmission power of the transmission line is proposed.

Key words: compact line； large surge-impedance loading power； transmission power； capacitance；