The embodiments of disclosure disclose a method and device for multiuser superposition transmission and a method and device for demodulating multiuser information transmission. In the method, two bit information streams are respectively modulated into a first complex symbol sequence and a second complex symbol sequence; superposition processing on the first complex symbol sequence and the second complex symbol sequence is performed to generate a third complex symbol sequence, wherein the third complex symbol sequence has a Gray mapping attribute; and a sending signal is formed according to the third complex symbol sequence, and the sending signal is sent to multiple receivers.