The effect of reaction environment on the self assembly process of an octahedron-shaped Pd6L8 capsule was investigated. Quantitative analysis of self-assembly process with H-1 NMR spectroscopy revealed that the self-assembly , pathway of the capsule was altered by solvent and a leaving ligand coordinating to the metal source, which are not the components of the final self-assembly. Solvents definitively determine the pathway of the self-assembly at a very early stage intermediates of the self-assembly. Contrary to the expectation that the weaker the coordination ability of the leaving ligand is, the faster the formation of the final assembly becomes, a leaving ligand with weak coordination ability tends to generate a kinetically trapped species to prevent the capsule formation under mild conditions.