Abstract: It is an impatient and critical problem in the reconnaissance of the ground fissures in Xi'an area to develop simply equiped geophysical detection method in order to massive cavation and accelerate reconnaissance process. A study of geologic foundation for application radon measurement technique in the reconnaissance of ground fissures in Xi'an area is described in the paper. And in combination with engineering experience about 10 years, the characteristics of radon anomaly and the effectiveness of radon measurement on the ground fissures in Xi'an area area analysed. The conclusion is that the effectiveness of radon measurement on the ground fissures in Xi'an area is about 80%.