RLS and LMS blind adaptive multi-user detection algorithm and multi-user detector was proposed to solve the problem of multi-user signal detection problem encountered in underwater acoustic communication networks. In simulation analysis, RLS and the LMS blind adaptive multi-user detector were designed and tested for synchronous and asynchronous multi-user communication process. The results of SIR comparison and MMSE comparison show that, both of the two methods can realize blind adaptive detection when any user change in multi-user communication, during this process, the training communication sequences are not needed. The RLS algorithm has about 5dB higher in SIR compared with LMS algorithm, and the convergence velocity of RLS algorithm is also higher than LMS algorithm when the communication users change. RLS algorithm has better ability in multi-user detection than that of LMS algorithm, and it has great attraction and guiding significance for solving the problem of multiple access interference (MAI) in multi-user communication.