In order to make it convenient for computer automatic synthesize,the automatic type synthesis of planar kinematic chains with modified Assur-group adjacency matrix is proposed. First of all,aiming at the known amount of the components,the active ones and the Assur-group,the diagonal elements with the different combination modes is solved according to the Assur-group theory. Then the synthesis method and concrete process is summarized and the selected Assur-group adjacency matrix is defined. The kinematic chains are subdivided in terms of 3 conditions of pole number,active pole and Assur-group type,meanwhile the isomorphism is estimated. As a conclusion,the method has better regularity,high efficiency and is beneficial to eliminate the rigid chains and reduce the calculation workload of isomorphism identification. Especially,the method can be applied to the automatic type synthesis for the planar mechanism kinematic chains with multiple links and multiple degrees of freedom. In addition,the success is achieved in the application on the type synthesis for the planar closed kinematic chains with 12 links and 12-below-links. Finally,the type synthesis method is demonstrated with the example of kinematic chains with 6 links and single degree of freedom.