The Muglad Basin is a Mesozoic-Cenozoic rift basin in central Africa. The Fula sag is a hydrocarbon-rich depression in the north of Muglad Basin. All of its traps are fault-related, such as faulted anticline, fault nose, fault horst, fault block. Based on the seismic data interpretation, we analyzed the geometric characteristics and developmental stages of faults, identified the main structural styles developed in the study area. At the same time, the tectonic evolution process of Fula sag since the Cretaceous was restored by compiling tectonic evolution sections. The results show that Fula sag can be divided into four tectonic layers, which are basement tectonic layer, first-rift tectonic layer, second-rift tectonic layer and third-rift tectonic layer. The strikes of faults from bottom to top at Fula sag regularly change, from NNW to NWW. The basement tectonic layer develops main faults, forming the tectonic framework in Fula sag; the first-rift tectonic layer develops many secondary faults; the second-rift tectonic layer and the third-rift tectonic layer become smaller in fault density and the fault displacement. The faults in the study area are En Echelon, parallel, “brush-like” or “braided” in plane, while domino, En Echelon, shovel fan in profile. There are three levels of faults, in which most of the first and second faults were formed in the Abu Gabra period. According to the extension rate of each faulted period, the faults’ active intensity in Fula sag has gradually bean weakened since the Cretaceous.