Abstarct: Among various geophysical methods, the GPR method by having higher resolution can better reveal a variety of subsurface anomalies at shallow depths. These subsurface targets are detectable by GPR method, subject to having a good contrast in electromagnetic characteristics with their surrounding medium. In this regard, the GPR method was used to investigate the internal fractures of Khaju Bridge in Isfahan, as well as determination of its composition and texture. Another reason of using this method is its non-destructive nature, which makes it harmless to this precious monument. The main goals of this thesis are to identify internal fractures as well as their trends and extensions, and to investigate the texture and materials used in the construction of the Khaju Bridge using the GPR method. Moreover in this thesis, geometry and structure of the Khaju Bridge have been studied. By achieving different lengths of GPR profiles and processing and interpretation of the GPR data in this study, we have been trying to achieve all those goals. The geometry and structure of the bridge were clearly and accurately detected by the GPR sections. There were also internal hyperbolic shapes into the ceiling of the Shahneshin building, which were not visible. The observation of all the pillars affects all the GPR sections passing the floor of the Khaju Bridge, has also led to the hypothesis that the bridge pillars have been first built in a blade shape and then, the other Parts of the bridge have been built on those pillars. The kinds of the materials used in the construction of the bridge using the method of hyperbola fitting was determined which were proved to be correct with good accuracy. The internal texture of the bridge was examined and it was found that in parts of the sections where the reflections were stronger, the texture was probably more compact. By comparison the fractures outcroped on the bridge with the GPR sections obtained, it is concluded that the fractures in these sections show themselves with a change in the GPR wave amplitude. This was used to identify the probable internal fractures of the bridge and their trends and extensions. The probable spreading of the outcroped fractures was also investigated. Indeed, due to the complexity of the materials used in the bridge structure and the existence of noise, it is difficult to identify and segregate fractures from other internal components of the bridge. In general, by examining the different sections of GPR profiles in the Khaju Bridge, it is concluded that the GPR method can be used to achieve the goals mentioned above and has an appropriate response to these goals.