Abstract: Rock strength is one of the important factors which affect roof stability and selection of support methods. To study the influence of different argillaceous contents on mechanical properties and failure characteristics of roof sandstone, three kinds of sandstone with different amounts of muddy were tested under uniaxial compression and Brazil splitting test through SHIMADZU AG-X250 electronic universal testing machine. The test results show that: the existence of mud weakens the strength of sandstone. In three kinds of sandstone, containing with a small amount and a big amount of argillaceous sandstone, whose uniaxial compressive strength is reduced by 22 % and 4 % respectively compared with those without argillaceous sandstone, in addition, the tensile strength reduced by 47 % and 45 %, respectively. The reduction range of compressive strength and tensile strength is not synchronous; the ratio of initial elastic modulus Ei and tangent modulus Et of three kinds of sandstone is calculated and counted. Containing with a small amount of argillaceous sandstone has biggest θ value, indicating that its internal fracture develops well; through analyzing the failure modes of three types of sandstone, it is found that the shearing failure is non-argillaceous sandstone, the longitudinal splitting failure is argillaceous sandstone, and the inclination angle of the fracture surface with a small amount of argillaceous sandstone is smaller.