Abstract: During the Three Gorges Projct，many complicated engineering and geological problens are met,high-resolution harmless detecting method is needed to find bured geological defect or engineering quality problems,to guarantee the project schedule and engineering quality. Georadar is applied in detecting the extension of inhomogeneous weatheriag of granite, mapping the extension and geomery of large faults and weathering alternative layers, checking the enginecring quality of expresses. 3 case histories are introduced.The detecting results are consistent to the real situations. The application effects are obvious.