Abstract: The 220 kV line longitudinal differential protection is the main technical means to ensure the safe operation of the power grid. With the increasing importance of the longitudinal differential protection business, higher requirements are also put forward for the communication technology of 220 kV line longitudinal differential protection service. The change from high frequency carrier channel to optical fiber transmission is the mainstream trend in the future. This paper first introduces the main communication methods and their advantages and disadvantages of the current 220 kV line protection, and then introduces the key technologies of IEEE C37.94 2 Mbit/s optical interface in detail, and designs a typical networking scheme of 220 kV line longitudinal differential protection communication network of the power grid. Finally, the actual engineering case is used to demonstrate the advantages and significance of the 220 kV line protection communication network based on 2 Mbit/s optical technology carrying longitudinal differential protection service from the test data such as bit error rate and time delay.