Different　nucleation　types　of　water　drops　were　summarized,　calculated　and　analyzed　on　the　basis　of　classical　nucleation　theory,　and　experiments　on　horizontal　cold　surfaces　were　carried　out　under　natural　convection　to　examine　the　influences　of　hydrophobic　surfaces　on　frost　formation.　Illustration　of　coefficient　functions　of　energy　barriers　of　different　nucleation　types　indicates　that　the　energy　barrier　to　nucleation　on　a　convex　surface　is　relatively　larger　than　that　on　a　concave　surface.　If　significant　influences　on　water　drop　nucleation　are　expected　of　foreign　surfaces,　the　ratio　of　the　size　of　the　foreign　nucleus　to　the　size　of　the　critical　nucleus　of　the　new　phase　should　vary　within　the　range　0-1.　If　this　ratio　is　larger　than　10,　there　is　no　distinction　for　different　heterogeneous　nucleation　types　of　water　drops.　The　experiment　results　show　that　when　there　are　no　observable　water　drops　develop　at　the　early　stage　of　frost　formation,　the　frost　crystals　on　the　hydrophobic　surface　are　even　denser.　If　deposition　of　ice　particles　is　dominant　after　frost　formation　starting,　the　frost　growth　on　the　hydrophobic　surface　and　untreated　surface　is　in　the　same　pattern.