A data transmission method performed by a mobility management entity, characterized by comprising: receiving a small data transmission parameter from a user equipment, wherein the small data transmission parameter comprises an indication of whether the user equipment supports small data transmission; determining a small data transmission policy according to the small data transmission parameter, wherein the small data transmission policy includes a notification of adoption of small data transmission optimization and a limit on a maximum number of times of transmission; sending the small data transmission policy to the user equipment; and performing the small data transmission with the user equipment according to the small data transmission policy; wherein the performing the small data transmission with the user equipment according to the small data transmission policy comprises: receiving a small data container sent by the user equipment, wherein the small data container comprises a bearer identification and an Internet Protocol, IP, packet corresponding to the bearer identification, and the IP packet includes uplink small data; and extracting the IP packet from the small data container, determining a tunnel endpoint identifier, TEID, of a serving gateway, SGW, and an Internet Protocol, IP, address of the SGW according to the bearer identification in the small data container, constructing the IP packet corresponding to the bearer identification into a GTP-U packet, and transmitting the GTP-U packet to the SGW according to the TEID and the IP address. receiving a small data transmission parameter from a user equipment, wherein the small data transmission parameter comprises an indication of whether the user equipment supports small data transmission; determining a small data transmission policy according to the small data transmission parameter, wherein the small data transmission policy includes a notification of adoption of small data transmission optimization and a limit on a maximum number of times of transmission; sending the small data transmission policy to the user equipment; and performing the small data transmission with the user equipment according to the small data transmission policy; wherein the performing the small data transmission with the user equipment according to the small data transmission policy comprises: receiving a small data container sent by the user equipment, wherein the small data container comprises a bearer identification and an Internet Protocol, IP, packet corresponding to the bearer identification, and the IP packet includes uplink small data; and extracting the IP packet from the small data container, determining a tunnel endpoint identifier, TEID, of a serving gateway, SGW, and an Internet Protocol, IP, address of the SGW according to the bearer identification in the small data container, constructing the IP packet corresponding to the bearer identification into a GTP-U packet, and transmitting the GTP-U packet to the SGW according to the TEID and the IP address. receiving a small data container sent by the user equipment, wherein the small data container comprises a bearer identification and an Internet Protocol, IP, packet corresponding to the bearer identification, and the IP packet includes uplink small data; and extracting the IP packet from the small data container, determining a tunnel endpoint identifier, TEID, of a serving gateway, SGW, and an Internet Protocol, IP, address of the SGW according to the bearer identification in the small data container, constructing the IP packet corresponding to the bearer identification into a GTP-U packet, and transmitting the GTP-U packet to the SGW according to the TEID and the IP address.