The excessively tilted fiber grating (Ex-TFG) is a novel fiber grating device with unique structure, which has the characteristics of orthogonal polarization coupling, high refractive index sensitivity, low temperature sensitivity and vector sensing response. Recent years, benefitting from the fact that Ex-TFG is sensitive to the surrounding environment refractive index, Ex-TFG has been widely investigated and applied in the field of biochemical sensing. Meanwhile, the non-circular symmetric evanescent field distribution of Ex-TFG provides the possibility for vector sensing applications. Based on the theoretical and experimental research, the basic theory and research progress of sensing characteristics of Ex-TFG are exhibited in detail in terms of basic coupled-mode theory of gratings and properties of transmitted cladding modes.