The assembly structure of Lennard-Jones model CCl4 molecules confined in a slit-shaped graphitic micropore of slit width (w,) of 0.8, 1.0, and 1.3 nm at 303 R was studied by Grand Canonical Monte Carlo simulation. The radial distribution functions (RDFs) for CCl4 molecules in pores having different widths were analyzed using snapshots of the molecular assemblies. The assembly of spherical molecules had a symmetrical packing structure that depended on the pore width. The coordination number and the intermolecular distance of each quasi-symmetrical structure were geometrically determined, and the RDF structure was assigned to each symmetrical structure. As we assumed a perfect symmetry on geometrical calculation, this approach was named "quasi-symmetry analysis". In the micropore system of w = 0.8 nm, adsorbed molecules form a rippled single layer having disordered close packed hexagonal structure. Though the molecules adsorbed in the micropore of w 1.3 nm formed a bilayer structure, the RDF was similar to that of the w = 0.8 nm system. In the system of w = 1.3 nm, each adsorbed layer has a close packed hexagonal structure without geometrical restriction from the opposite adsorbed layer. This structure is a bilayer two-dimensional liquidlike structure. The assembly of CCl4 molecules in the micropore of w = 1.0 nm had the bilayer structure of adsorbed molecules having a rectangular lattice. This molecular assembly had a face-centered cubic structure, coinciding with the structure of a plastic crystal phase. Only in this pore width system (w = 1.0 nm) do the molecules have three-dimensional regularity.