An automatic synthesis method for the topological structure of a series mechanism is proposed based on the theory of position and orientation characteristics（ in short,POC） set. The digital modeling of the topology structure of the series mechanism is built,and the flow chart and the main steps are given. Firstly,the series mechanisms are digitally described by using matrices. Then,the locations relationships among kinematic pairs are thoroughly enumerated by using the method of exhaustion,the automatically solving of position and orientation characteristics set is realized by using algorithm,the mechanism that meet the requirement is selected,and the GUI human-computer interaction interface is designed. The proposed automatic synthesis method is of universal significance,and the integrated mechanism is comprehensive that is convenient for the computer to analyze the automation of the mechanical system which make the automation be feasible.