Abstract: The detection of blind fault is important in various engineering construction. Based on the analysis of ground radon value formed in blind faults, we detect the blind fault in research area by using radon measurement, to calculate the anomaly threshold of radon value, divide the radon anomalies and explain the information of underground fault, both fractal theory and statistical method were used. The study found that fractal theory is more reasonable than statistical method in dividing the abnormal range; the tendency of blind fault can be initially estimated by the radon leptokurtosis near the surface.