Abstract: The development degree of macro cracks in rock mass has an important influence on the stability of karst bank slope in reservoir area. This paper aims to effectively detect and identify the geometric shape and distribution characteristics of macro cracks in rock mass. It adopts and simplifies the model of vertical cracks in rock mass in Wuxia typical karst bank slope of Three Gorges Reservoir area. It is based on the non-destructive GPR geophysical technology and uses theoretical analysis and numerical simulation. It studies the variation law of time distance curve and amplitude characteristics of cracks in radar echo profile when the width, length and inclination of vertical cracks in rock mass change. The results show that the radar echo response at the top and bottom of the fracture is hyperbolic, which can be used as a sign of fracture identification. The width of fracture is closely related to the maximum amplitude and energy mass of radar echo. The angle of fracture can affect the shape of radar echo energy mass. The field test results show that the ground penetrating radar with 900MHz antenna frequency can be used to detect the distribution of vertical macro cracks with centimeter width within the depth of about 1.5 meters inside the karst bank slope, and can be used as a monitoring means to investigate the macro crack propagation inside the rock mass of the bank slope in the reservoir water area.