One of the most effective raw materials for improving the resistance to slag and penetration is microsilica. Therefore, microsilica is widely used in industries. In this way, in this research, refractory samples based on alumina and bauxite containing 0, 0.5, 1, 2, 3 and 4% by weight of microsilica were examined and tested. The obtained results show that with the increase of microsilica up to 2%, there is a decrease in the rate of penetration. In the range of 2 to 3% of this material, corrosion has decreased, but with the increase of microsilica up to 4%, it was accompanied by an increase. Permeation resistance also increased slowly at values greater than 2%. The results of these tests showed that microsilica can increase the compressive strength by 60% and the tensile strength by 20%. Although the mechanical performance of refractory masses containing microsilica may be weakened due to its low melting point at high temperatures, this material is considered as a key factor in the design and manufacture of high alumina masses because it leads to the formation of an in-situ spinel phase, which is in the Patil layer. Steel industry is important.