A method of selecting a user plane gateway and a device of selecting a user plane gateway are provided. The method includes: receiving, by a CP function, a first data packet sent by a UE; selecting, by the CP function, based on the first data packet, a first target UP-GW for the UE. An UP-GW is selected for the UE when receiving the data packet sent by the UE, so as to enable the data transmission to better adapt to changes of the UP load and the network topology, thereby improving the data transmission efficiency.