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The ultrathinβ-Sn(001) films have attracted tremendous attention owing to its topological superconductivity (TSC),which hosts Majorana bound state (MBSs) for quantum computation.Recently,β-Sn(001) thin films have been success-fully fabricated via phase transition engineering.However,the understanding of structural phase transition of β-Sn(001)thin films is still elusive.Here,we report the direct growth of ultrathinβ-Sn(001) films epitaxially on the highly ori-ented pyrolytic graphite (HOPG) substrate and the characterization of intricate structural-transition-induced superstruc-tures.The morphology was obtained by using atomic force microscopy (AFM) and low-temperature scanning tunneling microscopy (STM),indicating a structure-related bilayer-by-bilayer growth mode.The ultrathin β-Sn film was made of multiple domains with various superstructures.Both high-symmetric and distorted superstructures were observed in the atomic-resolution STM images of these domains.The formation mechanism of these superstructures was further discussed based on the structural phase transition of β to α-Sn at the atomic-scale thickness.Our work not only brings a deep under-standing of the structural phase transition of Sn film at the two-dimensional limit,but also paves a way to investigate their structure-sensitive topological properties.