The　experimental　results　of　the　influences　of　the　boiling-condensation　surface　spacing　on　boiling　and　condensation　co-existing　phase　change　heat　transfer　characteristics　in　confined　space　under　low　heat　flux　conditions　are　presented.　The　working　medium　is　de-ionized　water,　the　phase　change　chamber　consists　of　a　copper　surface　with　an　extended　thin　film　to　restrain　the　edge　effect　as　the　boiling　surface,　a　polished　cooling　cooper　surface　as　the　condensation　surface　and　the　transparent　glass　tube　as　the　side　wall.　The　liquid　thickness　of　the　confined　chamber　with　a　48　mm　spacing　is　set　at　10　mm,　14　mm,　18　mm,　22　mm,　26　mm,　30　mm　and　34　mm,　respectively;　and　the　liquid　thickness　of　the　confined　chamber　with　a　18　mm　spacing　is　set　at　6　mm,　8　mm,　10　mm　and　12　mm,　respectively.　Experimental　observation　and　results　show　that　the　liquid　thickness　has　strong　influences　on　the　boiling　and　condensation　inside　the　chamber,　as　well　as　their　interactions.　The　interactions　have　direct　effects　on　the　heat　transfer　characteristic.　The　results　and　observations　also　disclose　that　there　always　exists　an　optimum　water　filling　amount　at　which　both　the　boiling　and　the　condensation　heat　transfer　coefficient　acquire　their　maximum　value　for　different　spacings.