Abstract: Selection of basis material is a key process for dual high energy X-ray computer tomography basis material decomposition method (BMDM). In order to make clear the influence of different basis materials on material discrimination accuracy and put forward a reasonable principle for the selection of basis material, this article compared the atomic number and electron density of materials being discriminated which were calculated with BMDM based on different basis materials. It further summed up a basis material selection principle named neighboring principle, i.e., choosing a basis material with the atomic number close to that of the material under discrimination could improve the discrimination accuracy, and four energy basis material decomposition methods are put forward based on the principle. Finally, with the Monte-Carlo technique, the validity of the four energy basis material decomposition methods was verified.