In　recent　years,　with　a　gradual　decline　of　teenagers＇　fitness　and　health　monitoring　data　in　our　country,　physical　health　of　teenagers　is　becoming　a　more　and　more　important　problem.　The　traditional　evaluation　method　can　test　teenagers＇　health　condition　by　spot　checks　every　year.　However　it　is　difficult　to　analyze　the　changes　of　the　teenagers＇　physical　data.　In　the　present　paper,　an　early　warning　system　of　physical　exercise　based　on　exercise　heart　rate　and　time　is　proposed.　The　system　classifies　the　intensity　of　movement　by　exercise　heart　rate　and　time,　and　then　calculates　the　load　and　the　score　according　to　the　evaluation　standards　we　put.　To　verify　the　maneuverability　of　the　evaluation　theory　model,　real-time　monitoring　of　heart　rate　during　physical　education　class　in　a　high　school　is　conducted.　Results　show　that　based　on　exercise　heart　rate　and　time,　the　score　of　teenagers＇　exercise　condition　can　be　obtained,　which　can　reflect　the　daily　exercise　of　each　person　intuitively.