In this work,basic oxygen furnace（BOF）slag was modified at high temperature with blast furnace（BF）slag by changing R（R=w（CaO）/w（SiO2））. The results showed that BF slag can effectively stabilize fCaO in BOF slag. When R is 1.5 and duration time at 1 500 ℃ is 30 min,the f-CaO elimination rate reached80.22%. Through X-ray diffraction and FESEM analysis,there were gehlenite,akermanite and pleonaste phases presented in the reconstructed slag. A positive correlation was established between the reduction in f-CaO content and the increase in gehlenite and akermanite contents.