Abstract: Straight, arc-like and broken lines on the remote sensing images are mostly related to linear geological structures, and may indirectly indicate the existence of underground faults. In this study, taking the Penglai area as a case, the Landsat 5 TM images of 1990 are used to extract linear structures based on the principles of remote sensing interpretation, image improvement technologies and interpretation signs. The techniques of histogram equalization, principal component analysis, filtering, and composite processing of DEM data are adopted to define those structures. 5 NNE major faults and 23 other faults are found in the Penglai area as the results.