Aiming at the problem of single parameter of traditional flow meter and problem of composite measurement of fluid flow and temperature, a composite flow and temperature sensor based on fiber Bragg grating is proposed. The pressure loss of fluid is reduced by using hollow cylindrical cantilever beam. The end cover, cantilever beam and target plate are processed in one body, which increases the stability of the sensor Firstly, sensing theory of fiber Bragg grating and flow-temperature are combined. The flow and temperature composite sensing theory based on fiber Bragg grating is studied. Then, the sensor that integrated target structure with the cantilever beam of hollow cylinder is designed. And its performance is simulated. Finally, the flow and temperature experimental system platform is set up. The sensing of temperature and flow experiments are carried out on the sensor. The results show that the relationship between temperature and wavelength shift is linear. The linearity is above 99%. The temperature resolution of the sensor is 0. 04℃ , the temperature measurement error is 1. 8%, the flow resolution is 0. 33 m 3 / h, and the flow measurement error is 2%. The fiber Bragg grating composite sensor can realize composite measurement of flow and temperature, and is expected to be applied to a flow measurement system requiring large-scale network detection, and has a good application prospect.