Understanding　the　relationship　of　the　Internet　latency　among　network　nodes　is　important　to　cope　with　the　problems　of　network　measurements.　There　are　some　researches　touched　on　this　point　but　seldom　explicit　studies.　In　this　paper,　we　study　the　similarity　among　the　network　nodes　based　on　RTT.　First　of　all,　we　check　the　effects　of　the　path　length　and　load　on　RTT,　and　then　conclude　that　they　may　affect　the　similarity　too.　Next,　study　the　effects　of　these　two　factors　on　the　similarity:　similarity　between　two　nodes　is　uptrend　when　their　public　path　length　gets　longer　or　public　path　load　gets　heavier;　similarity　is　downtrend　when　their　private　path　length　gets　longer　or　private　path　load　gets　heavier.　That　is　the　more　they　have　in　common,　the　more　similar　they　are.　©2010　IEEE.