The visualization of highly ordered adlayers of 5,10,15,20-tetrakis(N-methylpyridinium-4-yl)-21H,23H-porphine tetrakisi(p-toluenesulfonate)(TMPyP) on the iodine-modified Au(111) in 0.1 M perchloric acid solutions was achieved by in situ scanning tunneling microscopy(STM). TMPyP was found to form highly ordered molecular layers on the iodine-modified Au(111) substrate. High-resolution images of individual TMPyP molecules showed a typical square porphyrin ring with additional four bright spots around the ring. These bright spots are attributed to the pyridinium units.