Abstract: Based on deeply studying and analyzing Hilbert-Huang transform(HHT), a so-called semiperiodical -semi-symmetrical method is presented in this paper to deal with the boundary problem resulting in error during the process of the empirical mode decomposition(EMD).It is proved that this method is very valid and has high precision by many experiments of signal simulations and comparison between the results from this method and those from the EMD method.