The　effect　of　contact　angle　on　water　droplet　freezing　process　on　a　cold　flat　surface　under　natural　convection　conditions　was　experimentally　investigated.　A　series　of　hydrophobic　surfaces　with　different　contact　angles　were　prepared　by　solution　immersion.　The　contact　angles　of　these　surfaces　were　varied　from　97.2　degrees　to　154.9　degrees.　Comparative　observations　of　water　droplet　freezing　processes　were　carried　out　on　both　plain　copper　surface　and　these　hydrophobic　surfaces　under　the　same　conditions.　The　experimental　results　showed　that　the　contact　angle　has　a　strong　influence　on　the　water　droplet　freezing　time.　The　larger　the　contact　angle　is,　the　longer　the　freezing　time.　The　frost　crystals　growth　on　the　droplet　surface　that　frozen　on　the　hydrophobic　surface　is　faster　and　presents　a　pattern　that　is　more　dendritic　than　that　on　the　plain　copper　surface.　(C)　2012　Elsevier　Inc.　All　rights　reserved.