Low-temperature vaterite-type LuBO(3) (π-LBO) was prepared by a solid-state reaction method at high temperature. The reasoning of the existence of vacancy-stabilized π-LBO was investigated for the first time using neutron diffraction patterns, Fourier transform infrared (FT-IR) spectra, and high-resolution transmission electron microscopy. The results clearly demonstrated that the B and O vacancies in π-LBO came into being during the heating process. The existence of an open B(3)O(9) ring consisting of BO(3) and BO(4) units in π-LBO due to the B and O vacancies was demonstrated by FT-IR. The vacuum ultraviolet-ultraviolet spectroscopic properties of π-LBO were studied in detail. In addition, the luminescence mechanism of Ce(3+) in π-LBO was put forward and discussed with that of calcite-type LuBO(3) (β-LBO).