Abstract: Aiming at the problems of huge pressure loss, narrow measurement range and a complex structure of a fiber Bragg grating (FBG) flow and temperature composite sensor, this paper proposes a small FBG-based probe-type flow and temperature composite sensor. Firstly, based on the bending deformation theory of cantilever beams and the FBG sensing principles, the probe-type flow and temperature composite sensor model is established combined with the flow velocity distribution characteristics of the fluid in the pipeline, and the mapping relationship between the central wavelength drift and flow and temperature of FBG is revealed. Secondly, the strain distribution characteristics of the probe structure are studied by finite element analysis method, and the optimal sticking position of the FBG is determined. Finally, an experimental system platform is established, and temperature and flow sensing experiments are carried out. The results of the temperature experiment show that the temperature sensitivity of the sensor is 25 pm/℃, which is 2.3 times that of the bare FBG, and the repeatability error is 3.621%. The flow experiment results show that the measurement range of the sensor is from 2 m3/h to 30 m3/h, and the repeatability error is 2.141%. Compared with the existing FBG flow and temperature composite sensors, the proposed sensor has smaller pressure loss and wider measurement range