Abstract: Based on the median filtering algorithm, a method for extracting backscatter ionogram cleaning data is presented by reference to the characteristics of clutter and background noise in the ionogram. An algorithm of backscatter ionogram classification based the shape recognition theory by using the backscatter ionogram cleaning data is put forward, and the method to extract the shape factor are introduced. The simulation result show that the presented algorithm has the capacity of ionogram classification and a good prospect in applications.