Abstract: A method based on the model of propagation channel is proposed. In the method, Givens transform is used to calculate the expected information matrix step by step, ignore the irrelative results. In this way, the computational complex and memory needed are reduced. The method can be used without the preinformation of source number. The online structure of the algorithm makes it easy to be realized in parallel multi-DSP. Computer simulation verified the correctness and effectiveness of the method proposed.