The band structure of torsional vibration in a 2D discrete gyroscope phononic crystal was studied. The unit cell consists of a gyroscope, frame, and torsional springs. The governing equations of the unit cell and the dispersion relationship were derived using the angular momentum theorem and Bloch′s theorem, respectively, and the characteristics of band structure were also analyzed. The effects of critical parameters on the band structure, such as angular momentum, moment inertia, and torsional stiffness, were studied theoretically. Moreover, the band structure was also calculated by numerical method, and the results agree well with the theoretical prediction, which validates the existence of band gap in this phononic crystal.