Two　phase　flow　and　heat　transfer　characteristics　of　a　separate-type　heat　pipe　have　been　studied　experimentally　and　theoretically.　The　experimental　apparatus　have　the　same　geometry　for　the　evaporator　and　the　condenser　which　consist　of　5-tube-banks,　with　working　temperature　ranges　of　80-125A　degrees　C.　The　experimental　working　fluid　is　dual-distilled　water　with　corrosion-resistant　agents.　Heat　transfer　coefficients　for　boiling　and　condensation　along　with　heat　flux　and　working　temperature　are　measured　at　different　filling　ratio.　According　to　the　results　of　the　experiments,　the　optimized　filling　ratio　ranges　from　16　to　36%.　Fitted　correlations　of　average　heat　transfer　coefficients　of　the　evaporator　and　Nusselt　numbers　of　the　condenser　at　the　proposed　filling　ratio　are　obtained.　Two　phase　flow　characteristics　of　the　evaporator　and　the　condenser　as　well　as　their　influence　on　heat　transfer　are　described　on　the　basis　of　simplified　analysis.　Reasons　for　the　pulse-boiling　process　remain　to　be　studied.