For the problem of user pairing in uplink non-orthogonal multiple access （NOMA）， this paper proposes a NOMA user pairing scheme based on bilateral matching model. Different from the existing NOMA user pairing scheme， this scheme adopts pre-grouping according to the user channel gain， so as to avoid the user pairing with large channel gain gap. At the same time， users with small channel gain difference can be avoided to improve the overall performance of the system. Considering that users with too small channel gain cannot communicate in the real scene， a threshold value of channel gain is set as the decision condition of whether the communication can be achieved. After grouping， the channel gain difference is used as the preference degree for pairwise pairing between groups. The simulation results show that compared with the traditional NOMA pairing scheme and the classical orthogonal multiple access （OMA） network， the proposed scheme can effectively improve the traversal and speed of the system. The proposed scheme is still superior to other schemes when the threshold value of channel gain changes.