A　kind　of　new　warm　mix　additive　called　SAP　was　proposed　in　this　paper.　The　principle　is　using　foam　to　lower　the　operating　temperature　of　asphalt　mixtures.　The　mixing　and　molding　temperature　of　SAP　warm　mix　asphalt　mixture　were　measured　by　viscosity　method　and　void　ratio　method,　which　are　almost　20　degrees　C　lower　than　that　of　HMA.　Considering　the　engineering　applications　and　test　accuracy,　the　void　ratio　method　is　considered　to　be　the　better　way　to　measure　the　operating　temperature　of　asphalt　mixtures.