The secondary ion mass spectrometry (SIMS) was applied to measure the trace element abundances in majorite and the ultramafic liquid equilibrating at high pressure and temperature for the first time, and was proved to be useful for the high pressure experimental petrology. The analysis by SIMS was made to determine the abundance of 15 lithophile elements (Li, Be, B, Sc, Ti, V, Cr, Mn, Y, Zr, La, Sm, Gd, Yb, and Hf), one siderophile (Co), and two chalcophile elements (Cu, Zn). The electron microprobe (EPMA) analysis was also made to obtain the major element abundance. Some lithophile elements (Al, Be, and V) are enriched in majorite, whereas the lithophile elements (Li, B, Na, K, Ca, Ti, Zr, Y, La, Sm, Gd, and Hf), and siderophile and chalcophile elements (Co, Cu, Zn) are favored in the liquid. These results give important constraint for the genesis of komatiites and chemical heterogeneity in the Archean mantle.