The protection channels between the power cable and overhead power line are mainly fiber channel and high frequency transmission channel. The right choice between the two channels needs to be made according to the actual power line. Based on the characteristic of mixed power line, this paper expatiates how to make the choice between the fiber channel and high frequency channel, and analyses the application of the two channels on mixed power lines, especially, it discusses the application of high frequency transmission channel in high voltage mixed line, this paper can provide a reference for the feasibility study on the selection for protection channel in mixed power lines.