Abstract: Compared with the traditional central tube submarine fibre optical cable, the stranded submarine fibre optical cable can hold more fiber cores, however, due to the limitation of the drum of the cable-former, the continuous production of the long section of the stranded submarine fibre optical cable cannot be realized.A kind of long-length stranded submarine fibre optical cable and its transition joint were proposed.The performance of the transition joint was verified by tensile test, flexion test, torsion test and hydrostatic pressure test.The influence of the transition joint on the performance of the laminar stranded submarine cable was verified by tensile test, impact test, crush test, repeated bending test, bending under tension test and temperature cycling test.The test results showed that the performance of the long-length stranded submarine fibre optical cable with transition joint meets the standard requirements and meets the requirements of engineering application.