In the design stage of the core structure of a pressurized water nuclear reactor,a model experimental device is usually used to verify the thermal characteristics.Synchronizing measuring temperature,strain and vibration of the electrically heated simulated fuel rods in the device is an important part of studying the hydraulic parameters of the core rod bundle channel.In this paper,the research of fiber sensing method based on double fiber Bragg grating (FBG) is to solve the problems of traditional detection methods,such as weak anti-electromagnetic interference ability,large volume,and single parameter can be measured only.Firstly,the wavelength drift coefficient of the two FBGs on the rod body is changed by using the optimized design of the optical fiber package to realize the reliable decoupling of strain and temperature sensing,therefore the measurement crosstalk problem of the two parameters is resolved;Then,by dynamically collecting the FBG center wavelength,the acquisition of the vibration characteristics of the fuel rods is analyzed in the frequency domain,and the precise measurement of the three parameters is achieved finally.Experiment results measured by this method show that the vibration amplitude caused by the flow increases monotonically with the flow rate in the flowing water bath environment,and the measurement error rate of the rod surface temperature and strain is less than 0.5%,which can provide reliable data support for the research and design of the reactor.