With the popularization and rapid development of mobile intelligent terminals (MITs), the number of mobile applications, or apps, has increased exponentially. It is in-creasingly common for malicious code to be inserted into counterfeit apps, which can cause significant economic damage and threaten the security of users. Code obfuscation techniques are a highly efficient group of methods for code security protection. In this paper, we pro-pose a novel control flow obfuscation based method for Android code protection. First, algorithms to insert irrelevant code and flatten the control flow are employed that minimize the cost of obfuscation while ensuring its strength. Second, we improve the traditional methods of control flow flattening to further reduce the costs of obfuscation. Lastly, the use of opaque predicates is strengthened by estab-lishing an access control strategy, which con-verts the identification of opaque predicates in the entire program into a graph traversal prob-lem, and thereby increases the strength of the code protection. We did some experiments to evaluate our method, and the results show that the proposed method can work well.