Polyaniline with different morphologies doped by sulfuric acid were prepared using rapid mixture method. Scanning electron microscopy analysis showed that morphologies of polyaniline can be changed from unequal particles to nanowires with increasing the molar ratio of aniline to ammonium peroxydisulfate. The isomerization of -pinene were regarded as the goal reactions to study the effects of morphologies of polyaniline on the catalytic activities. The results proved that morphologies of polyaniline have a little effect on selectivity, but obviously affect the conversion rate of -pinene. The polyaniline nanowires hold the best catalytic activity among polyaniline with the three kinds of morphologies. The thermal behaviour of PANI was also investigated in detail by using a dynamic rate mode of thermogravimetric analyser (TGA) in inert atmosphere, and the results show that the polyaniline wires have good thermal stability.