It is provided a method for constructing a graph representation for a 3D object, wherein comprising the steps of generating an initial graph representation for the 3D object, wherein a node in the initial graph representation corresponds to a component of the 3D object and a symmetric indication value uniquely identifying a symmetric group is associated with a symmetric node; selecting two nodes from one symmetric group that has the most symmetric nodes, wherein the distance between the two nodes are the largest among distance between any other two nodes within the symmetric group; obtaining two set of nodes by expanding separately from the two nodes to their directly connected nodes, wherein if a node is connected directly to both two nodes, the node is excluded from the two set of nodes; and if determining that the two sets of nodes match, updating the graph representation by grouping each set of nodes into one node.