In order to solve the mode mixing problem encountered in the standard EMD (empirical mode decomposition), an improved EMD method is suggested in this work. In the method, a masking signal selected by optimization according to ener gy method is composed with the signal to be decomposed; then the composed singna l is decomposed by using EMP mehtod. In this way, the mode mixing phenomenon cou ld be eliminated. The method also allows EMD to be used to separate components t hat are si milar in frequency that would be inseparable with standard EMD techniques. E xperimental results show that the method suggested in this work is practica l and effective.