A series of novel 2,2'-bipyridylene-contaning polymers are synthesized through the Wittig reaction. Some of these polymers show a highly selective affinity toward Mg2+ in a mixture of alkaline metal ions, which is different from the 2,2'-bipyridylene-containing poly(phenylene vinylene) derivatives reported previously. This is the first case to demonstrate materials show a selectivity toward Mg2+. The structures of the polymers may play a crucial role for this selectivity.