Because of the wide range of the light source spectral width and optic al fiber Bragg grating sensing wavelength mobile range,the number of multiplexed fiber Bragg gratings in th e fiber grating sensing system is greatly limited.If there are too many fiber gratings,it will cause the interfe rence between the codes in the fiber.In order to solve this problem,in this paper,we propose the method of th e time delay localization,which uses the time delay of the sensing signal to locate the sensing fiber Bragg gratings.We des ign a time delay auxiliary positioning optical fiber Bragg grating sensing system.This system works on the basis of field－programmable gate array (FPGA).It works with the demodul ation through the combination of F-P cavity and time delay localization method and processing the data through FPGA.In accordance with the system design,we have built up an experimental system and carried out a simple experiment.We present the exper imental results,which show that the method can increase the number of multiplexed gratings and it is practical and highly accurate.