A data transmission method for increasing a success rate of receiving multicast service data by a terminal device by repeated transmission of first control information, second control information, third control information, and change notification, comprising: receiving, by the terminal device, system information sent by a base station device, wherein the system information is used to control repetition of the second control information and the system information includes configuration information required by the terminal device for completing reception of the multicast service data; receiving, by the terminal device, the change notification sent by the base station device, wherein the change notification is used to notify that the first control information changes, and the change notification is scrambled by a first radio network temporary identifier, RNTI, receiving, by the terminal device, the second control information sent by the base station device, wherein the second control information is scheduling information of the first control information and is used to control repetition of the first control information being control information of the multicast service data; receiving, by the terminal device, the first control information sent by the base station device, wherein the first control information is used to control repetition of the third control information being scheduling information of the multicast service data; receiving, by the terminal device, the third control information sent by the base station device, wherein the third control information is used to control repetition of the multicast service data; and receiving, by the terminal device according to the third control information, the multicast service data sent by the base station device. receiving, by the terminal device, system information sent by a base station device, wherein the system information is used to control repetition of the second control information and the system information includes configuration information required by the terminal device for completing reception of the multicast service data; receiving, by the terminal device, the change notification sent by the base station device, wherein the change notification is used to notify that the first control information changes, and the change notification is scrambled by a first radio network temporary identifier, RNTI, receiving, by the terminal device, the second control information sent by the base station device, wherein the second control information is scheduling information of the first control information and is used to control repetition of the first control information being control information of the multicast service data; receiving, by the terminal device, the first control information sent by the base station device, wherein the first control information is used to control repetition of the third control information being scheduling information of the multicast service data; receiving, by the terminal device, the third control information sent by the base station device, wherein the third control information is used to control repetition of the multicast service data; and receiving, by the terminal device according to the third control information, the multicast service data sent by the base station device.