The principle of multi_resolution analysis (MRA) is introduced in the paper.so does its fast algorithm.The method of how to select or construct a basic function is discussed in principle.A basic function in MRA space is selected in terms of the characters of super elevation rate signal.A real_time filtering algorithm for flowing data is also presented by using MRA,then it is compared to a conventional filtering method via the processing of simulation and real data.Efficiency of the MRA algorithm is demonstr...