Buffering capability based on the slow light properties of silicon-polymer photonic-crystal coupled cavity waveguide (SP-PC-CCW) was set forth. We focused on reducing the dispersion and enhancing the buffering capability, including storage capacity, storage time, and physical size of each bit by appropriately adjusting the radii of the silicon filled rods in the first, second rows of the polymer-photonic-crystal slab, and the radius of the central cavity. We fulfilled the highest favorable value of the longest storage time of about 554.60ps and the highest storage density as 0.125464 bit/μm which is 1.72 times of the highest reported in PC-CCW micro-optical buffer. A polymer is used for the future incorporating electro-optic effect in buffers to realize dynamic controlling of optical properties. The results have been validated by the finite-difference time-domain (FDTD), in which a higher Q value resembles a longer buffering time of field inside the cavity. Moreover, the accumulation process of energy in the cavity contributes to the delay time, and thus higher quality factor corresponds to longer accumulation time, leading to more delay time. The proposed SP-PC-CCW may find applications in micro-integrated optical circuits for optical-signal processing, all-optical communication, and optical computers.