Optimization design is conducted for the connection of the composite insulator and the line hardware in suspension string, strain insulator string, L-shaped string, V-shaped string, reverse V-shaped string of the overhead transmission lines. The metallic ball and ball socket on both ends of the composite insulator are changed into round haplopore and bolt connecting structure, which removes the R-shaped fitting pin and realizes bolt connection with hardware. The manufacturing process of terminal hardware becomes simpler. Two or more inner-arc U-shaped hoops are used for one or both terminal hardware in direct connection with the composite insulator, which increases the axial rotation freedom of the composite insulator in suspension string, strain insulator string and V-shaped string, avoids any end torsion of composite insulator, and guarantees its mechanical behaviors. Through this work, the transmission line will operate more safely and reliably and the goal of full-life operation of overhead transmission line will be attained.