Abstract: Present state of urban active fault survey is reviewed. Some problems of unban active fault fine locating by using 2D seismic exploration are presented, such as poor controlling of small-scale structures in middle-shallow strata, insufficient precision of fault homing in steeply dipping strata, inaccurate fault location coming from oblique intersection between surveying lines and fault strike due to existing buildings and other obstacles, and inadequate constrain on fault breakpoint, intersection position and endpoint due to sparse surveying grids. Advantage of 3D seismic exploration is analyzed theoretically. The problem of inaccurate fault location, induced by limitation of 2D seismic exploration, surface environment and geological conditions, can be solved by using 3D exploration. The feasibility and significance of using 3D seismic exploration in urban region is demonstrated through example analysis in data acquisition, instrument selection, geometry design, optimizing design, field quality monitoring, special data processing and good geological effects.