Abstract: Magnesium oxide plays a crucial role in the progress of blast furnace production. In this paper the effect of magnesium oxide on the green ball quality and cruslring strength of acid pellets had been investigated through changing the content of magnesium oxide by adoption of A fine powder,B fine powder and light burned dolomite. It was found out that with the increase of magnesium oxide content,the compressive strength and falling strength of the green ball firstly decreases and then increases,and its thermal explosion temperature firstly increases and then decreases,the change of the green ball quality is mainly related to mineral powder foundation properties such assurface area. The compressive strength of pellets after roasting reduces with the increase of the magnesium oxide content since a portion of the Mg atoms move into hematite and replaces the Fe atoms in crystal,and the strength of Mg-O bond is lower than the strength of Fe-O bond. At the same time,a few magnesium oxide get into the slag phase and destroy the silicate network structure,which improve the liquidity of the slag phase. Parts of the slag phases are dispersed into hematite between grains,other slag phases gather together,the gap between slag phase and hematite becomes more border with the decrease of temperature,resulting in the decrease of compressive strength of the pellets.