Four fully optimized geometries of (HN_3)2 by the ab initio method at the HF/6-31G level are Obtained, and the intermolecular interaction energy is calculated with MP4SDTQ electron correlation correction and basis set superposition error correction. The computed results indicate that N_3H…NHN2 is the most stable one of the four optimized (HN3)2 structures and its intermolecular interaction energy is -- 16. 07 kJ• mol--1.