Investigations　into　the　thermal　characteristics　of　glass-water　heat　pipes　from　0　A　degrees　C　to　60　A　degrees　C　were　carried　out　at　the　National　Institute　of　Metrology　(NIM),　China.　In　this　paper,　studies　on　a　glass-water　heat　pipe　with　four　thermometer　wells　are　described.　The　experimental　results　indicated　that　the　temperature　stability　and　uniformity　of　the　thermometer　well　of　the　glass-water　heat　pipes　are　within　several　tenths　of　a　millikelvin　when　the　heat　pipes　are　immersed　in　a　constant-temperature　liquid　bath,　since　they　have　a　highly　effective　thermal　conductivity.　They　are　able　to　maintain　a　constant　temperature　by　the　absorption　or　liberation　of　the　latent　heat　of　evaporation　to　attenuate　temperature　fluctuations　of　the　surroundings.　Also,　above　0　A　degrees　C　to　30　A　degrees　C,　the　temperature　stability　of　the　thermometer　well　of　the　glass-water　heat　pipe　is　better　than　0.1　mK　for　approximately　16　h.　The　maximum　temperature　differences　among　the　thermometer　wells　are　less　than　5.5　mK　when　the　water　heat　pipes　operate　in　the　range　from　0　A　degrees　C　to　60　A　degrees　C.　Therefore,　water　heat　pipes　are　very　promising　to　improve　the　performance　of　liquid　baths　and　to　accurately　calibrate　thermometers　by　comparison.