One dimensional linear polyaniline (PANI) tubes (with cavity about 2-3 nm) and three dimensional dendritic PANI fibers (with different length) have been synthesized by chemical oxidation polymerization of aniline doped with stearic acid at room temperature. The shape of the as-prepared PANI could be easily tuned from line to dendriform and to network simply by controlling the concentrations of aniline and stearic acid. Scanning electron microscopy and transmission electron microscopy were applied to investigate the various kinds of morphologies. UV-vis absorption spectra and Raman spectra suggested these as-prepared PANI were in conductive emeraldine state and the various kinds of structures could affect their property.