Abstract: The problems of synchronization and control of Duffing system with uncertain parameters are considered.Firstly,the synchronization and control problems are discussed when the system parameters are known.Secondly,the same problems with unknown system parameters are considered.Since it is difficult to deal with this problem directly,the vector of adjustable parameters,which can be obtained by using the developed adaptive law,is introduced to replace the unknown parameters in the control law.Thirdly,theoretical proofs are given to show that the controlled goal can be achieved using the presented control law.Finally,several simulation examples are presented to show the effectiveness of the proposed method.