In this work, we systematically investigated the morphologies of polymers prepared by chemical oxidation of aniline and methyl-, methoxy-, or ethoxy-substituted aniline under the same experimental conditions. No matter the presence or absence of 10-camphorsulfonic acid (CSA), the oxidation of aniline produces nanotubes, while the oxidation of most aniline derivatives produce hollow microspheres under the same experimental conditions. These results illustrate the oligomers with phenazine-like structures produced at the initial oxidation of aniline are crucial for the formation of PANI nanotubes. The formation mechanism of the hollow microspheres of PANI derivatives is discussed. The main factors to control the polymer morphology are stability of droplets of aniline and its derivatives formed in an aqueous solution and the rate of exothermal reaction. The fast exothermal reaction benefits the formation of uniform microspheres. We also suggest that the hole on the surface of microspheres forms at the initial oxidation stage and is maintained by the flux of water and water-soluble components in the course of polymerization.