A blind multi-user detection algorithm (BMUD) which is suitable for multi-path-fading Channels based on Lagrange neural network (LNN) is proposed. Based on the minimum output energy (MOE) criterion, the blind detection algorithm is formulated as a constrained optimization problem inherently and is then resolved efficiently using the neural network. Compared with the previous RLS(recursive least squares )-MOE blind detection algorithm or for multi-path channel, the BMUD based on LNN has better performances: lower computational complexity, faster convergence speed and capability in the multi-path-fading channel. The bit error rate (BER) and signal-to-interference-and-noise ratio(SINR) performances of the detection algorithm in multi-path channel are close to that in single path channel.