A two-dimensional sheet assembly of a hexameric hemoprotein was constructed. A single cysteine residue was introduced onto each subunit surface in the hexameric hemoprotein and modified with a maleimide-tethering tripeptide FGG tag to provide a host-guest interaction between one cucurbit[8]uril molecule (CB8) and two FGG tags. The addition of CB8 into the engineered protein forms the assembly as a sheet-like precipitate. High-speed atomic force microscopic measurements directly reveal the detailed structure and the dynamic process of formation.