In this theoretical study, a photonic crystal coupled-cavity waveguide created on polymer substrate was demonstrated to provide high-performance slow light with low group-velocity dispersion and large normalized delay–bandwidth product. Combined with structural-parameter optimization, the normalized delay–bandwidth product was enhanced to a large value of 0.809, and the group-velocity dispersion was on the order of 10 4 ( p s 2 / k m ) . Furthermore, the optimized coupled-cavity waveguide had tunability capabilities by changing the external pump laser power. Importantly, while adjusting the slow light, the normalized delay–bandwidth product values remained above 0.8, which was necessary to maintain the performance of optical buffering devices.