Abstract: Aiming at the integrated representation of aboveground and underground,indoor and outdoor objects,full 3D spatial index is urgently required.Existing R-tree methods are usually limited by their disadvantages such as the critical overlay of sibling nodes and the uneven sizes of nodes.In order to solve this problem,k-even algorithm is introduced and the sum of overlap and overlay volume is employed as the grouping criterion,which improve the spatial cluster grouping and R-tree insertion algorithms,and therefore evidently reduce the overlap of R-tree sibling nodes and even the size of nodes.