Measurement,whichiscalledmetrologyinancienttimes,istheimportantfoundationofsocialdevelopmentofthemoderncountries’economy,scienceandtechnology.Ithasalonghistoryandplaysanimportantroleinnationalwelfareandthepeople'slivelihood.Establishedin221BC,intheQindynasty,Qinshihuangunifiedweightsandmeasures,andbecameaunifiedsystemforthemeasurementofmilestoneinancientChina.OnMay20th,1875,thesigningoftheconventiononmetric,openedupaworldwidetoimplementneweraofmoderninternationalsystemofunitsofmeasurement.Basedonquantumphysics,researchandapplicationofmodernmeasurementscienceandtechnology,providesmoreaccuratemodernmetrologytechnicalsupportforthedevelopmentofhumancivilization.In1999,the21stinternationalconferenceonmeasurementmadeadecisionthatsince2000,May20isfor"WorldMetrologyDay".China'spropagandathemeof2015isinlinewithinternationalthemefor"measurementandlight".