Anti- B18H22 (n-B18H22) is a new class of laser materials. In this paper, n-B18H22-β-cyclodextrin (β-CD) supramolecular inclusion complex was prepared by saturated aqueous solution method for the first time. The characterization of the inclusion complex was studied by FTIR, XRD, and SEM. The results showed that the stability of n-B18H22 in water was greatly enhanced due to the formation of the inclusion complex. This paper has opened a new way to improve the stability and extend the application of n-B18H22 in aqueous solution. The inclusion compound has potential applications in the preparation of borane liquid laser and the synthesis of n-B18H22 derivatives.