This application discloses a cable, a cable assembly, and a communications system. The cable includes a power wire, a signal wire, a ground wire, a wrapping layer, a coaxial wire, and a protective layer. The signal wire is used to transmit a low-speed signal. The coaxial wire is used to transmit a high-speed signal. The power wire, the signal wire, and the ground wire are wrapped in the wrapping layer. The coaxial wire is on an outer side of the wrapping layer. The wrapping layer and the coaxial wire are wrapped in the protective layer.