A series of aromatic ether diamines having different numbers of benzene rings, different amino-substituted positions and different moieties in their structures was synthesized. By using these synthesized ether diamines and commercially available tetracarboxylic dianhydrides, various kinds of polyimides having almost the same molecular weights were synthesized. The glass transition temperature (T-g) values and thermoplasticity were studied by focusing on the chemical structures of their repeating structure units. It was shown that T-g and melt-processibility of polyimide depended on the chain length and meta-linkage contents of ether diamine, and the difference of amino substituted position in ether diamine.