The co-channel interference exists in the uplink multiuser multi-relay cooperative systems. In order to deal with it, a blind signal detection scheme based on parallel factor (PARAFAC) model is proposed in a Co-Channel Interference DS-CDMA cooperative system. A trilinear alternating least squares (TALS) algorithm is applied in the PARAFAC model. The feasibility of this proposed scheme and the data range of each parameter are analyzed. Compared with constant-modulus (CM) blind detection algorithm, this proposed scheme has stable fitting result, as well as better detection performance in channel and signal estimation. Simulation results corroborate the effectiveness of our scheme in terms of channel estimation accuracy and biterror-rate.