Image scrambling is an available means for image encryption.Since chaos system is extremely sensitive for initial value

ergodic and aperiod

it was widely applied for image encryption.Because there are certain techniques to decode the encryption method based merely on chaos system

a novel scrambling method based on image blocking and chaos system is presented in this paper.The rough idea of this method is that an image is scrambled by a blocking method

and then the result is further scrambled by a modulating way provided by chaos system.The experimental result proves that the new method is effective.