Abstract: Defects within rocks have a significant influence on the mechanical properties of the rock material. By uniaxial compression experiments on sandstone samples containing single prefabricated holes, the effects of hole shape on strength and failure modes of sandstone samples were analyzed. The mechanisms of variation in the strength of sandstone samples containing differently shaped holes were also explored by using a 2D software for rock failure process analysis, RFPA^2D. The results show that the load capacity and elastic modulus of sandstone samples containing pre-fabricated holes are significantly lower than those of intact ones. Sandstone samples containing square holes have the lowest bearing capacity, while those containing diamond-shaped holes have the highest. The final failure of sandstone samples is mainly caused by tensile stresses which are different for the different geometrical shapes of hole-defects, and the final failure modes mainly include shear failure, tension destruction, and mixed tension-shear failure. The structural effects caused by hole-defects also have some effects on the peak strength and crack propagation of sandstone samples containing a single hole.