The dehydrogenation of poly(1,3-cyclohexadiene)-polystyrene binary block copolymers was investigated. The dehydrogenation of the poly(1,3-cyclohexadiene) block, which was composed of 1,2-cyclohexadiene (1,2-CHD) and 1,4-cyclohexadiene (CHD) units, was strongly affected by the polymer chain structure. The 1,2-CHD units prevented the dehydrogenation. The rate of dehydrogenation was fast on a long sequence of 1,4-CHD units, whereas it was relatively slow for 1,2-CHD/1,4-CHD (≈1/1) unit sequences. The bonding of the polystyrene block to the polymer chain effectively improved the rate of dehydrogenation. The dehydrogenation of a poly(1,3-cyclohexadiene) block containing a small amount of 1,2-CHD units progressed via step-by-step reactions.