Abstract: Through processing and analyzing of microseism signal monitored by ARAMIS microseism monitoring system in Yuejin Coal Mine, the paper obtains development laws of power spectrum before and after rock burst. The results present that the power spectrum value of microseism signal is lower before and after rock burst with the corresponding big value distributed at the frequency range of 50 to 150 Hz, while the value variation at a same frequency range length is higher；when rock burst happens, the power spectrum is evenly distributed at different frequency ranges and the value, especially the corresponding with higher and lower frequency, increases while the value variation at the same frequency range length decreases.