Molecular-based dielectric switching materials are special crystal–crystal structure phase transition materials, and play an important role in multifunctional materials and other fields. In this paper, a trivalent cyclic amine is used as the building unit to successfully prepare a molecular crystal material, 1,4,7-triazacyclononane trihydrochloride, 1, with abundant hydrogen bonds and high temperature dielectric switching properties, and its IR, TGA, DSC, VT-PXRD (variable-temperature PXRD), VT-structures, and T–ε′ (temperature dependence of the real part of the dielectric constant) are characterized and analyzed. The space group of 1 is P2₁/n at 298 K and Rm at 403 K. Two endothermic peaks appeared near 369 K and 380 K and one exothermic peak appeared near 363.5 K in the DSC heating–cooling cycle test. In the vicinity of the corresponding phase transition temperature, 1 shows an obvious reversible change of dielectric plateau and small dielectric loss. The dielectric switching cycle curves show that 1 has good dielectric switching performance. All of these interesting physical properties are closely related to the reversible order–disorder states of cations and anions in the molecule. This work shows that 1 is a switchable dielectric molecular crystal material with broad application prospects, and provides a new route for design and synthesis of switchable dielectric materials with excellent properties.