Numerous Cr-bearing ultramafic rock masses with high ore-prospecting potential are distributed around Luobusha, the largest chromite deposit in China. The Zetang rock mass was selected to conduct profile probing using gravimetric, magnetic and magnetotelluric methods. The results show that the Zetang rock mass was cut into several parts by approximately NS-trending faults, with the west parts moving farther northward than the east ones and distributed in NWW directions on the whole. The magnetic anomalies in the mass were caused by the magnetite resulting from the serpentinization and the residual magnetization when the rock mass was formed, and such magnetic anomalies indicate the limits of the superficial part of the rock mass.