The morphology of polyaniline, poly(o-toluidine) and poly(2-ethylaniline) synthesized under various conditions were studied. The morpholgy of the polymer is controlled by the rate of consuming electric quantity. When the rate of consuming electric quantity is slow, fibrous structure was formed. While the rate of consuming electric quantity is fast, short fibers with amorphous material or granular structure were formed. Substituents have a large effect on the morphology of the polymer. As the substituent group becomes larger, the regular packing of the polymer can not be obtained, the fibrous structure can hardly be formed.