The interfacial properties of hydrate and its ambient play an important role in hydrate technique. In this paper, the molecular characteristics of H₂O in hydrate/ice/liquid water mixture system are investigated based on molecular dynamics (MD) simulations. The structure I (sI) methane hydrate is partially heated to obtain the studied system. The properties including hydrogen bond, radial distribution function (RDF) and F3 order parameter (tetrahedral coordinated parameter of H₂O) indicate that there is little difference of water structure in the hydrate region and ice/liquid water mixture region. The F4 order parameter (parameter based on H–O–O–H torsion angles of H₂O) could be used to distinguish the different region. The value of F4 experiences the continuous change at interface between mixture region and hydrate region.