Finite　element　method　is　applied　for　the　calculations　of　temperature　fields　of　concrete　filled　steel　tubes　under　fire.　A　theoretical　model　that　calculates　deformations　and　strength　of　beam-column　in　fire　and　fire　resistance　is　described　in　this　paper.　A　comparison　of　results　calculated　using　this　model　with　the　results　of　tests,　there　is　good　agreement.　Based　on　the　theoretical　model,　influence　of　the　changing　strength　of　the　materials,　sectional　dimensions,　steel　ratio,　load　eccentricity　and　slenderness　ratio　on　the　fire　resistance　is　discussed.　The　theoretical　model　in　this　paper　were　used　to　provide　data　on　the　necessary　fire　protection　measures　for　the　concrete　filled　steel　tubular　columns　used　in　a　high-rise　building,　SEG　Plaza　in　Shen-Zheng　City,　South　of　China.