In order to meet the growing demand for different applications, great efforts have been made to develop new energetic materials with high energy and good safety. Fused cyclic energetic material, a special category of pi-conjugate structures containing two or more rings, typically exhibits excellent performance and is currently a key focus of research. In this paper, we have designed and synthesized a new tricyclic, fused energetic material: 5-amino-[1,2,5]oxadiazolo[3,4-e]tetrazolo[1,5-c]pyrimidine 1-oxide (3). The reaction mechanism of the one-step reaction, including nucleophilic substitution and cyclization, has been theoretically investigated. Notably, compound 3 has a high density (1.864 g cm(-3)) at room temperature and good detonation properties (D-v: 8391 m s(-1) and P: 28.2 GPa). Compound 3 has a relatively low impact and friction sensitivity (IS > 40 J, FS > 300 N), and acceptable thermal stability (T-d: 175 degrees C), demonstrating the great potential of compound 3 as a high-energy, insensitive tricyclic fused energy-containing material.