The　steel　roof　of　a　gymnasium　is　a　hybrid　tension　structure　with　pre-stressed　truss　shell　system.　The　finite　element　method　was　used　to　analyze　the　mechanical　behavior　of　the　roof　structure　under　temperature　rising　and　cooling.　The　results　show　that　high　temperature　results　in　the　yielding　of　structural　components　and　the　development　of　plastic　deformation;　significant　residual　stress　and　deformation　are　observed　after　the　temperature　drops　to　room　temperature.　Temperature　rising　and　cooling　incurs　large　support　reactions,　which　is　harmful　to　the　structure,　especially　when　the　temperature　rising　and　cooling　occurs　in　the　central　area　of　the　roof　structure.　Hence,　flameproof　should　be　paid　more　attention　for　the　central　area　of　the　structure.