The invention relates to the technical field of communication and signal processing, in particular to a Group-CDMA communication method and a system. The method is characterized in that all users are divided into G groups, and a code division multiple access way is used for distinguishing between the groups; an interleave division multiple access way is used for distinguishing between users in a group, and the dispreading operation is used for eliminating set-up interference and the stepwise iteration is used for eliminating multiple access interference between the users at a receiving end; and the structural complexity and calculation complexity of a receiver are linear with the number of users in groups. The simulation study shows that the invention can effectively improve the communication capacity and spectral utilization rate and strongly promote the application of MUD in MS, and has remarkable advantages of low complexity, high reliability and the like.