Optical fiber gratings have become one of the most important devices in the field of optical fiber sensing and optical fiber communication. Because of the novel characteristics, cascaded structures of the fiber gratings have always been the focus of research. The research progresses of cladding mode recoupling, edge filtering and independent cascading of the fiber Bragg grating-long period fiber grating (FBG-LPG) cascaded structure are summarized, and their technical difficulties are discussed. Suggestions for improvement are presented. To address the problem of the complexity of transmission type FBG-LPG optical path, a reflection type FBG-LPG independent cascaded structure which can effectively simplify the structure is proposed, and the system performance is optimized and verified by experiment. The development trend of the FBG-LPG cascaded structure is predicted.