Abstract: Aiming at the security problem of software white box，an improved parameterized decomposition tree-based obfuscation method with double flattening control flow is put forward． On the basis of given upper bounds of depth，breadth and granularity，the method builds a decomposition tree，coordinates the whole tree with a cycle se-lection structure named while-switch，and then applies double flattering to relevant nodes that satisfy certain condi-tions． Experimental results indicate that，in comparison with the flattening obfuscation method of control flow on the basis of parameterized decomposition tree，the proposed method reduces the execution expense and solves the deep nonfeasance problem; and that，in comparison with the traditional method only with flattening control flow，the pro-posed method increases the difficulty in decompilation and reverse engineering．

Key words: software protection, control flow flattening, code obfuscation, reverse engineering, decomposition tree, security