Abstract: Due to special characteristics of conductor structure and production process, radiation cross-linked flexible cables are susceptible to flattening by external forces in production process.For radiation cross-linked flexible cable with the sixth type conductor structure, conductor structure, production process, retracting and pulling devices on roundness of cables in process of each production process were studied.M ain influencing factors of flattening was analyzed.Conductor structure, tension parameter, production device and process were improved, in order to improve the roundness of cables.