To understand deformation mechanisms of non-basal slip in magnesium, [1010] tensile tests were carried on pure magnesium single crystals in various temperatures. While the crystal fractured as brittle manner at room temperature, the crystals were deformed by {1011}<1123> first order pyramidal slip and showed ductility above room temperature. Yield stress due to the first order pyramidal slip showed high temperature dependence. These results indicate that high ductility of magnesium at high temperature would be caused by activation of first order pyramidal slip.