In view of problems existing in the detection of the traditional hydraulic syst em,a new one-piece target type flow sensor is designed and researched based on fiber Bragg grating (FBG).This paper proposes a compact structure, which is easy to process,install and dismantle,based on the analysis of the principle of FBG.This one-piece target type structure transforms the force of target put in flui d flow into the FBG wavelength drift with a corresponding relationship,and this FBG target type flow sensor ef fectively solves the problem on the cross sensitivities of the temperature and strain by using double FBGs symmetrically p asted on the both surfaces of the cantilever.By many experiments,the feasibility and reliability of the design are verified,sensitivity of sensor is 3.55pm/g,and the corresponding flow sensitivity is 0.076L/s.The results of exp eriments show that the dual FBG wavelength changes in the amount and the quality of the load on the target piece have a good linear relationship, the sensitivity is twice of that of a single FBG,and almost not influe nced by environmental temperature.