Abstract The stability, geometric structure and electronic properties of a novel body-centered tetragonal carbon allotrope Bct C8 are systematically investigated. Bct C8 are formed by sp3-bonded carbon atoms and can be regarded as a compressed bundle of carbon nanotubes (CNT). The transition path from CNT to Bct C8 has been simulated, indicating a possible approach to synthesize Bct C8. The X-Ray diffraction, phonon and Raman spectroscopies are presented as reference for experimental studies. Besides, Bct C8 is a semiconductor with an indirect gap of 1.66 eV and will transform to semimetal when doping with boron and nitride atoms. Furthermore, considering its porous structural character, the lithium storage capability of Bct C8 are also discussed, a directional fast lithium-ion mobility with a rather low 0.04 eV barrier is revealed. Therefore, the Bct C8, once synthesized experimentally, would have fruitful applications in carbon-based electronics and energy storage.