Abstract:MgO is important composition of BF slag and metallurgical properties was improved when the slag viscosity lowered, the fluidity raised , the reducibility, softening and melting temperature all raised as slag contains a certain amount of MgO. The permeability of stock column of BF was improved as low temperature reduction degradation index was decreased with containing a certain amount of sinter MgO. In the current conditions , in this industrial experimentation, the results showed that mine-phase structure and mineral composition were improved, the tumbler index increased 0.10% about, RDI from 66.03 % decreased to 64.33 %, but degree of reduction from 84.46% lowered to 84.13%,sinter size became smaller a little. At the same time, the content of MgO of BF slag to increase 0.35 % reached 7.8-8.0%,the meltability temperature and viscosity of slag reduced, the fluidity of slag from 115mm impromed to 170mm, the iron loss from 7.09% decreased 5.15%, pig iron yield decreased 18t/d ,and comprehensive coke ratio declined 6.57kg/tp by indexes correction, effects of saving coke was significant ,and technical parameters of sinter and BF were optimized and improved,so that the content 7.8-8.0%of MgO of BF slag is suitable level.