To investigate aerodynamic performance of Flapping Wing Micro Air Vehicle (FWMAV), it is significant to design an efficient test system for measuring aerodynamic performance of FWMAV in hovering condition. In this study, a test platform with a simple trigger device, which can synchronously obtain data including forces, wing motion and power consumption under a certain flight status of uncontrolled FWMAV, was introduced. Time-resolved forces generated by wing flapping were measured by an ATI force transducer and the wing kinematics was tracked by a high-speed camera. A customed circuit was designed for power consumption. For simple experimental operation, a low- level signal was used to trigger our system for data acquisition, data processing and data storage. A flapper with 20cm wing span, which weighs 9.37g without batteries, was tested to characterize its aerodynamic performance through this platform. Test results show that the wing flapping frequency of the flapper can almost reach 13Hz at the flapping angle of 180° producing 8.1g maximum mean lift and 0.27g maximum mean thrust, which can provide valuable references for performance improvement and validation of aerodynamic modelling of FWMAV.