Isomorphism identification of kinematic chain topology graphs is a world puzzle.A new approach is presented to solve it.Kinematic chain topology graphs are depicted with character arrays based on the characteristic of kinematic chain topology graphs.The number of binary links in the limbs of topology graphs is arranged in group according to links with multi points of connection.The order of limbs in the groups can change and the order of links with multi points of connection outside the groups also can change,thereby forming character arrays.Characteristic of topology graphs is depicted with character arrays.This representation is straightforward and not affected when drawing modes and labeling ways change in topology graphs.Isomorphism of character arrays is defined in virtue of the concept of character string.The realization principle of program with Visual Basic is presented.Identification matrix is constructed to identify isomorphic character arrays.Two topology graphs are isomorphic only when the sum of every row and the sum of every column in identification matrix are nonzero simultaneously.Finally,case study proves that the approach is accurate,simple,efficient and easy to realize on a computer.The solution of the problem of isomorphism identification lays a foundation for mechanism type synthesis.