The paper proposes and proves three theorems of location reference point placement based on the analysis of the location error produced when an unknown node is located using the multilateral localization method.Therefore the location error can be reduced through purposive placement of the reference points in the ubiquitous computing environment.The location reference point selection algorithm is proposed.This algorithm bases on the relative position of reference points and selects the optimum reference points to locate the unknown node.The simulation experiment results indicate that the location reference point placement theorems & selection algorithm can meet the requirement of mobile node's real-time location in the ubiquitous computing environments and possesses the preferable location precision.