The invention discloses an unmanned aerial vehicle flight data recorder and a power failure detection and RAM (Random Access Memory) data protection method. Flight data are input through an RS232 or RS422 serial interface, and internally recorded data can be read out at a high speed through a USB (Universal Serial Bus) interface or an internal storage interface; during running of an unmanned aerial vehicle, data from the serial interface of an unmanned aerial vehicle flight control computer can be recorded and saved, so that the power failure signal of a system can be monitored under the disaster situations of control absence and crash of the aerial vehicle or abnormal cutoff of a power supply and the like, and all received data are record immediately. After a flight accident, the unmanned aerial vehicle flight data recorder installed in the unmanned aerial vehicle can be found, data saved therein are read out, and strong evidence can be provided for the analysis of flight accidents of the unmanned aerial vehicle. After conventional flight processes, data recorded can be taken as a strong basis for improving and designing a flight control rate. The unmanned aerial vehicle flight data recorder has the advantages of small size, low power consumption, light mass, high environment resistance and high data storage rate.