Based on the Th, Nb and Zr data of basalts formed in the typical tectonic settings of the world, we studied the principle of the geochemical discrimination of tectonic settings of basalts. The basalts of different tectonic settings are obviously different in the terms of Th, Nb and Zr. The types of tectonic settings are classified using the ratios between Th, Nb and Zr. A Th/Zr-Nb/Zr diagram is proposed to divide basalts of a series of tectonic settings, such as the margin of divergent oceanic plates, margin of convergent plates, oceanic plate interior, continental plate interior, and mantle plume.