Abstract: In this artical, the self-adaptive principle, first issued in the Computational Fluid Mechanics, is applied to the study of scale separation.The recovering coefficient of each scalesystem is not a constant (i.e.each to be recovered to the same extent) like that used in the conventional method, but is determined according to its magnitude of variation relative to the scale system to be separated, which may then be more efficiently concentrated near the maximum responding wavelength, avoiding the false growth caused by the same extent recovery.