For　urban　non-point　source　pollution,　different　kinds　of　subarea　have　different　pollution　characteristics.　We　take　an　urban　campus　as　our　study　subarea.　The　research　work　includes　underlying　surface　dividing　and　sampling　point　selecting,　sampling　apparatus　designing　and　installation,　runoff　pollutants　examination,　results　analysis.　The　author　obstained　423　samples　from　9　different　underlying　surfaces　and　1　natural　rainfall　during　rainwater　runoff　process　during　recent　3　years.　The　monitoring　water　quality　constituents　are　water　temperature,　PH　value,　dissolved　oxygen,　electrical　conductivity,　turbidity,　suspended　solids,　alkalinity,　ammonia　nitrogen,　total　nitrogen,　total　phosphorus,　total　organic　carbon,　chemical　oxygen　demand,　total　hardness,　Ca(2+),　Mg(2+),　sulfate,　heavy　metal,　and　so　on.　The　program　has　obtained　more　than　5000　chemical　test　data.　The　research　result　indicates　that:　the　main　pollutants　in　the　campus　are　COD,　suspended　solids　and　TN.while　the　concentrations　of　heavy　metals　and　inorganic　substances　are　relatively　very　low,　according　to　the　rainwater　quality　monitoring　data　collected　in　Beijing　University　of　Technology　and　Xidawang　Road　by　our　research　team　in　recent　years.　Furthermore　we　provided　a　statistical　method　for　determining　the　first　flush　time.　For　the　roof　underlying　surface　in　the　research　campus,　the　first　flush　time　is　10　minutes.