Abstract: Methods for auto-identification of propagation modes from backscatter ionograms are presented. The method first introduced is only based on a backscatter ionogram not requiring other sounding data. Through the mechanism of ionospheric propagation, the method can auto-identify what reflection layers (E layer, Es layer and F layer) exist in a backscatter ionogram without manual operation. And the leading edges for all existed layers are extracted with different algorithms. Finally, an interpretation method for a backscatter ionogram with the assistance of a vertical ionogram and an oblique ionogram is put forward. The method can improve the precision of mode identification and leading edge extraction in a backscatter ionogram and has a good prospect for application.