A data transmission device, wherein the data transmission device is applicable to a multi-stream data transmission system for line of sight propagation, the data transmission device is first communications equipment, the system comprises the first communications equipment and second communications equipment, both the first communications equipment and the second communications equipment comprise multiple antenna ports, and the second communications equipment is mobile communications equipment; and the data transmission device comprises: an obtaining module, configured to obtain a first antenna port corresponding to location information of the second communications equipment, wherein the first antenna port is an antenna port, of the first communications equipment, satisfying a condition for multi-stream data transmission between the first communications equipment and the second communications equipment, and the location information of the second communications equipment comprises a line of sight transmission distance between the first communications equipment and the second communications equipment and/or information about a relative angle between the first communications equipment and the second communications equipment; and a transceiver module, configured to perform multi-stream data transmission with the second communications equipment according to the first antenna port; wherein the transceiver module is further configured to receive antenna port information reported by the second communications equipment according to the location information of the second communications equipment, wherein the antenna port information comprises a quantity of first antenna ports and/or a sequence number of the first antenna port; and is determined by the second communications equipment according to the location information of the second communications equipment and a distance between second antenna ports of the second communications equipment and the obtaining module is specifically configured to determine the first antenna port according to the antenna port information obtained by the transceiver module. an obtaining module, configured to obtain a first antenna port corresponding to location information of the second communications equipment, wherein the first antenna port is an antenna port, of the first communications equipment, satisfying a condition for multi-stream data transmission between the first communications equipment and the second communications equipment, and the location information of the second communications equipment comprises a line of sight transmission distance between the first communications equipment and the second communications equipment and/or information about a relative angle between the first communications equipment and the second communications equipment; and a transceiver module, configured to perform multi-stream data transmission with the second communications equipment according to the first antenna port; wherein the transceiver module is further configured to receive antenna port information reported by the second communications equipment according to the location information of the second communications equipment, wherein the antenna port information comprises a quantity of first antenna ports and/or a sequence number of the first antenna port; and is determined by the second communications equipment according to the location information of the second communications equipment and a distance between second antenna ports of the second communications equipment and the obtaining module is specifically configured to determine the first antenna port according to the antenna port information obtained by the transceiver module.