Due to high-frequency flapping motion, the insect-inspired flapping-wing micro air vehicles(FMAV)present the characteristics of flexible and large deformation, nonlinearity vibration, force-torque coupling, etc. The lift force and torque generated by IFMAV is about mN and μN·m respectively, but it is difficult to accurately test small force and torque, which brings challenges for the structure design and control of the FMAV. In this paper, a novel force-torque sensor for the IFMAV is presented, which can measure the high-frequency lift force and torque generated by the IFMAV under fixed constraints. The lift-torque senor is designed to use a symmetrical multi-cantilever compliant mechanism to convert lift force/torque into a small deformation. Combined with a high-bandwidth, high-precision capacitive displacement measuring device, it can collect data of lift force/torque under high-frequency vibration conditions. In this paper, the sensor mechanics modeling is based on the beam theory, and it is verified by finite element simulation. The structure is designed and processed based on the main parameters of the IFMAV. Experimental test indicate that such features as the lift measurement range of -10~10mN, torque measurement range of -20~20μN·m, characteristic frequency of 1kHz, and the sensitivity of lift and torque of 0.01mN and 0.01μN·m respectively, were obtained. This sensor meets the test requirements of IFMAV which weights between 80~250mg and works in the range of 1~200Hz frequency.