A vehicle to everything, V2X, service message sending method, comprising: receiving, by a terminal device, communications interface configuration information from a network-side device, wherein the communications interface configuration information comprises interface indication information, and the interface indication information is used to indicate at least one communications interface used to send a V2X service message; determining, by the terminal device based on the communications interface configuration information, one communications interface from at least two communications interfaces used to send a V2X service message; wherein the at least two communication interfaces used to send a V2X service message comprise a PC5 interface and a Uu interface, and the interface indication information is used to indicate at least one of the PC5 interface and the Uu interface; the interface indication information indicates at least one communications interface, the at least one communications interface comprises the PC5 interface and the Uu interface, and the communications interface configuration information further comprises a communications interface trigger condition for determining the PC5 interface or the Uu interface; and the determining, by the terminal device based on the communications interface configuration information, one communications interface from at least two communications interfaces used to send a V2X service message specifically comprises: determining, by the terminal device, one of the PC5 interface and the Uu interface as the communications interface when determining that the communications interface trigger condition is met; and sending, by the terminal device, the V2X service message through the determined one communications interface. receiving, by a terminal device, communications interface configuration information from a network-side device, wherein the communications interface configuration information comprises interface indication information, and the interface indication information is used to indicate at least one communications interface used to send a V2X service message; determining, by the terminal device based on the communications interface configuration information, one communications interface from at least two communications interfaces used to send a V2X service message; wherein the at least two communication interfaces used to send a V2X service message comprise a PC5 interface and a Uu interface, and the interface indication information is used to indicate at least one of the PC5 interface and the Uu interface; the interface indication information indicates at least one communications interface, the at least one communications interface comprises the PC5 interface and the Uu interface, and the communications interface configuration information further comprises a communications interface trigger condition for determining the PC5 interface or the Uu interface; and the determining, by the terminal device based on the communications interface configuration information, one communications interface from at least two communications interfaces used to send a V2X service message specifically comprises: determining, by the terminal device, one of the PC5 interface and the Uu interface as the communications interface when determining that the communications interface trigger condition is met; and sending, by the terminal device, the V2X service message through the determined one communications interface. the at least two communication interfaces used to send a V2X service message comprise a PC5 interface and a Uu interface, and the interface indication information is used to indicate at least one of the PC5 interface and the Uu interface; the interface indication information indicates at least one communications interface, the at least one communications interface comprises the PC5 interface and the Uu interface, and the communications interface configuration information further comprises a communications interface trigger condition for determining the PC5 interface or the Uu interface; and the determining, by the terminal device based on the communications interface configuration information, one communications interface from at least two communications interfaces used to send a V2X service message specifically comprises: determining, by the terminal device, one of the PC5 interface and the Uu interface as the communications interface when determining that the communications interface trigger condition is met; and sending, by the terminal device, the V2X service message through the determined one communications interface. determining, by the terminal device, one of the PC5 interface and the Uu interface as the communications interface when determining that the communications interface trigger condition is met; and sending, by the terminal device, the V2X service message through the determined one communications interface.