A high-capability micro-optical buffer (MOB) based on a hexagonal cavity in a photonic crystal waveguide is investigated. The MOB is proposed by breaking the translational symmetry of the periodicity three times after introducing different types of cavities. In each time, we attained ultrahigh group index and highly Q-factor with highest delaying time. Ultrahigh group index of 21030 is obtained with Q-factor of 4309, delaying time of 70.1 ns, and buffer capacity of 8.41 bit. On the other hand, the bit rate and storage density turn into 117.73 Gb/s and 0.06121 bit/µm, corresponding to approximately 16.33 µm occupied by 1 bit for optical communication wavelength. Coupling a number of different types of cavities, higher Q-factor than that of an individual cavity can be obtained. It is shown that by coupling two cavities, the Q-factor is heightened to be 1.748 × 105 in low translational-symmetry case. We proposed a structure for promising application in optical signal processors and random access memories. Furthermore, we get longer delaying time and high Q-factor, which have important applications in low-threshold lasers, high fnesse flters and high-speed switching.