The invention discloses a multi-user information co-channel sending method and device, and a multi-user information co-channel receiving method and device. The multi-user information co-channel sending method comprises following steps: dividing N users into K groups; generating L superposition symbols according to the modulation symbols of each piece of user information in each group, wherein the K, N and L are integers, the L is more than or equal to K, the K is more than or equal to 1, the N is more than or equal to 2, and the L is not equal to 1; separately carrying out spread spectrum extension on the L superposition symbols by using different sequences in L orthogonal sequences with lengths of L, thus obtaining L symbol sequences; combining the L symbol sequences, thus obtaining combined symbol sequences; and sending transmitting signals formed by the combined symbol sequences. Through the methods and the devices of the invention, the problem that during NOMA downlink sending, in an actual fading channel, the risk of error propagation is great if symbol-level SIC is performed in the demodulation process of the terminal, which causes performance degradation, is solved; and the access performance is improved.