Self-assembling behavior of dibutyldisulfide (DBDS: CH3(CH2)(3)SS(CH2)(3)CH3) molecules on Au(1 1 1) was investigated with a combined system of high-resolution electron energy loss spectroscopy (HREELS) and scanning tunneling microscopy (STM). We observed two stripe phases with different stripe periodicities with STM, depending on the density of DBDS on the surface for the first time. At very low exposure of DBDS (0.5 L), STM showed that DBDS formed fragmentary chains and the periodicity of the stripe chains was about 2.1 nm. At exposure of 5 L, the periodicity of the stripe chains converged to 1.38 nm. In this phase, DBDS is lying clown on the surface and the C-C-C plane of the alkyl chain is parallel to the surface. At the saturation coverage, the molecular structure changes to a densely packed c(4 root3 x 2 root3) structure, that is the superstructure of root3 x root 3R30 degrees, containing bright and dark spots.