Triaxial compression test was carried out to study effect of fine content on shear strength of coarse grained soil. Siliceous sand and wetted glass beads were used as coarse sand and fine content, and they were mixed in mould to make specimen. It is found that the increase of ratio of glass beads decreases the internal friction angle under constant void ratio of siliceous sand, and that the dependency of shear strength on confining pressure decreases with the increase of ratio of glass beads. The modified internal friction angle for dilatency at failure depends on the weight ratio of glass beads and siliceous sand. Finally, we propose a prediction method for the measured internal friction angle by using the relationship between confining pressure and the dilatency coefficient at failure.