Abstract: using the gradient probability of crustal vertical deformation rate as the variable, the multifractal properties of several areas where strong earthquake occurred were studied, including Tangshan area, Hexi area and Beijing area. The result s show that Dq value ranges of multifractal spectra widen, that is, the Dq values in the-qside climb up, and those in the+q side drop down one to several years before strong earthquake occurrence. It suggests that the strengthening process of deformation distribution from sub-inhomogeneity to inhomogeneity ( complexity ) before earthquake occurrence is common or repeatable. So, it can be inferred that the anomaly of deformation field complexity strengthening maybe a qualitative precursory index for strong earthquake prediction.

Key words: Deformation field, Multifractal, Inhomogeneity, Strong earthquake