Interference cancellation is one of the key technologies in wireless optical code division multiple access (CDMA) systems. The principle and performance of blind multi-user detector algorithm based on recursive least square (RLS) are analyzed, and it is applied to wireless optical CDMA using optical orthogonal code (OOC). The selecting principle of forgetting factor, the convergence and error rate performance caused by forgetting factor are discussed. A RLS blind multi-user detection algorithm is proposed using variable forgetting factor. The forgetting factor is modified. The results show that the system using the improved method can get faster convergence speed and tracking speed of convergence and the estimation error is smaller. The signal to interference ratio is improved from 6 dB of the traditional algorithm to 9 dB. The RLS algorithm with variable forgetting factor is suitable for the wireless optical CDMA system using OOCs, and the performance of tracking the desired user signal is very good.