Bionic flapping-wing robots have become a global research hotspot because of their considerable potential in military and civilian applications. Measuring and analyzing the flapping deformation characteristics of flapping-wing robots are important for improving their flight performance， and these are challenging research topics in the field of flapping-wing robots. The existing measurement methods include numerical simulation， stereovision camera， and structured light projection measurement. There are problems with these techniques； e.g.， it is difficult to determine the boundary conditions， and visual occlusion occurs. Therefore， a dynamic deformation measurement method of contact flapping wing based on a fiber Bragg grating is proposed in this paper. A fiber Bragg grating flexible sensor based on a polyimide film is designed. The flexible sensor is arranged on the flapping-wing surface in the form of an array to monitor the real-time strain of the surface. The real-time strain data are reconstructed into the real-time three-dimensional （3D） shape of the flapping wing by using a reconstruction algorithm based on curvature. The strain variation of the wing surface in a stable flapping period is monitored. Then， a 3D deformation analysis is performed. The results indicate that the flapping-wing surface strain mainly occurs around the support rod， and the maximum value in the flapping stage is –50.6 με and 98.1 με， respectively. The deformation of the flapping-wing surface mainly occurs at the trailing edge of the wing surface， and the maximum values of flapping down and flapping up are –2.06 and 4.02 mm， respectively. This study provides a new measurement idea and technique for the dynamic deformation measurement of flapping wings. Deformation monitoring under outdoor flight conditions will be performed later to provide a scientific basis for improving the flight performance of ornithopters.