Abstract: Compared with the traditional unipolar submarine fibre optical cable, bipolar submarine fibre optical cable has two independent power supply lines, which can supply power to two different underwater systems simultaneously.In order to solve the key technologies of bipolar submarine fibre optical cable, the structure design of bipolar submarine fibre optical cable was studied, and the key technologies such as insulation structure design technology, joint technology and test technology of bipolar submarine fibre optical cable were broken through. The development of bipolar submarine fibre optical cable and its matching injection joint box has filled the domestic blank of bipolar undersea optical cable.