Abstract: A genetic programming(GP) based approach was developed for the synthesis of complex distillation systems.Combining with the knowledge of chemical engineering, some evolutionary functors were improved, and a set of special encoding method and solution strategy was put forward according to the characteristics of the complex distillation system.The flow scheme of the complex separation could be expressed directly by using GP’s special hierarchical structure and the problem of different meanings encountered by other stochastic algorithms for expressing distillation system could be solved.Without any superstructures of distillation system, the feasible region could be looked for automatically.The solutions of examples demonstrated that the optimized synthesis problems of complex distillation system could be solved rapidly with the improved algorithm, and the optimal configurations of thermally coupled(linked)side columns，fully thermal coupling column(Petlyuk column)as well as heat integration between the different columns could be searched automatically.