Embodiments of the present application provide a data transmission method. The method includes: sending, by user equipment, uplink data to a base station by using an uplink user equipment relay; and receiving, by the user equipment, downlink data from the base station, or receiving, by the user equipment, downlink data from the base station by using a downlink user equipment relay. Uplink transmission and downlink transmission are separately performed in different transmission paths, so as to reduce impact of a fault of a user equipment relay on a network, and improve network reliability.