Compositional inhomogeneity of the needle_exsolution magnetites in olivine from Bixiling garnet peridotite was recognized by means of map analysis using electron probe microanalysis (EPMA). Some needle-exsolution magnetites have relatively high Cr concentration, whereas others have relatively high Ti concentration. It is suggested that the distribution of titanium and chromium might have been inhomogenous in the original β -olivine-phase, resulting in the compositional difference observed in the needle_exsolution magnetites. This implies that the olivine originally existed as spinel-phase which was stable in the mantle. The present study therefore provides valuable information for determining the formation depth of the garnet peridotite and for understanding the mechanism of continental subduction.