Researching on chaos-based image encryption scheme is becoming increasingly popular; unfortunately, most of the algorithms proposed provide poor security because of their failure to resist attack. A new digital image encryption scheme based on variable parameters double Logistic systems is presented. The subkey sequences are generated after optimizing and adjusting from the chaotic maps which have certain relation to the plaintext, which enhances the security of the cryptosystem. The analysis and the simulation results imply this encryption scheme possesses the features of large key spaces, sensitive key dependence, and good security. Especially this algorithm is able to effectively resist traditional attack.