A substitution box (S-box) plays an important role in cryptographic algorithms.The design of S-box using chaotic systems has attracted a great deal of attention in recent years.A new method for obtaining cryptographically strong S-boxes based on spatiotemporal chaotic system is proposed in this paper.The discretized Baker map and affine transformation are used orderly by an algorithm to shuffle the table generated by the spatiotemporal chaotic system.The cryptographical properties of these S-boxes such as bijection,nonlinearity,strict avalanche,output bits independence and equiprobable input/output XOR distribution are analyzed.The results of numerical analysis show that the S-box designed by this method can against several attacks and all the criteria for designing good S-box can be satisfied approximately.More strong S-boxes can be obtained by this method with the change of the original conditions or control parameters of the spatiotemporal chaos system.Furthermore,our approach is suitable for practical application in designing cryptosystem.