Heavy　metal　contamination　of　water　has　become　an　important　problem　in　recent　years.　Most　hazardous　heavy　metals　exist　in　environmental　water　in　trace　or　ultra-trace　amounts,　which　requires　establishing　highly　sensitive　analytical　methods.　In　this　research,　quantitative　analyses　were　performed　using　high-resolution　continuum　source　graphite　furnace　atomic　absorption　spectrometry　combined　with　cloud　point　extraction　(CPE)　to　determine　Pb,　Cd,　Cu,　and　Ni　levels　in　environmental　surface　water.　By　optimizing　the　CPE　conditions,　the　enrichment　factors　were　29　for　Pb,　Cd,　and　Cu　and　25　for　Ni.　The　limits　of　detection　(LOD)　were　0.080,　0.010,　0.035,　and　0.014　mu　g　L-1　for　Pb,　Cd,　Cu,　and　Ni,　respectively.　The　sensitivity　of　the　method　is　comparable　with　those　reported　in　previous　investigations　using　various　methods　and　improves　outcome　by　2　to　3　orders　of　magnitude　compared　with　the　LODs　of　the　current　national　standard　methods　of　China.　Our　method　was　used　to　determine　Pb,　Cd,　Cu,　and　Ni　in　55　water　samples　collected　from　the　Tonghui　River,　which　is　the　principal　river　in　the　urban　area　of　Beijing,　China.　The　results　indicated　that　the　distributions　of　the　four　heavy　metals　in　the　Tonghui　River　were　related　with　the　environments.　The　levels　of　Pb　and　Ni　exhibit　increasing　trends　along　the　river　from　upstream　to　downstream　possibly　due　to　the　existence　of　some　chemical　factories　in　the　downstream　area.　Lead,　Cd,　Cu,　and　Ni　averaged　13.9,　0.8,　46.8,　and　38.5%,　respectively,　of　the　total　amount　of　the　determined　heavy　metals.　The　levels　of　the　four　heavy　metals　conformed　to　the　Environmental　Quality　Standards　for　Surface　Water　(Grade　I)　of　China.　This　work　provides　a　reliable　quantitative　method　to　determine　trace-amount　heavy　metals　in　water,　which　lays　a　foundation　for　establishing　standards　and　regulations　for　environmental　water　protection.