The　full-scale　fire　tests　of　three　RC　columns　under　axial　load　were　carried　out　with　standard　heating　curves.　The　immediate　reactions　and　collapse　states　of　tested　columns　were　analyzed　and　the　temperature　distribution　of　sections　and　axial　deformations　were　measured.　The　degradation　of　bearing　capacity　of　RC　columns　was　found　mainly　on　the　following　respects:　the　degradation　of　concrete　strength,　the　increase　of　axial　deformations　and　the　destructions　of　working　performances.　Computer　simulation　compiled　by　author　was　done　using　the　finite　element　method.　The　numerical　results　agree　well　with　test　data.　A　simplified　calculation　formula　is　put　forward　for　RC　column　bearing　capacity　under　fire,　which　is　proved　to　be　reliable　according　to　the　comparisons　between　test　record　and　calculation　results.