In conventional design of transmission lines, independent column foundation is individually allocated to each leg of tower. By analyzing the transmission tower foundation forces, four separate columns are united as a whole, the uplift and down force of foundations transmitted by cross beam, and the uplift force calculation is changed to bending force calculation. Furthermore, this design principles and methods of self-balanced cross foundation are introduced, and some issues of design features and process discussed. The self-balanced cross foundation is compared with other foundations, of which the applicability and shortcomings are analyzed. It is found from the calculations that the self-balanced cross foundation has the advantages of shallow depth, high reliability, perfect integrity, strong ability to resisting horizontal displacement, and better economy. Therefore it is worthy to be popularized, especially for the foundation designs of special geological conditions.