In order to store the data of the engine state during the flight of the UAV, an external Flash memory based on DSP TMS320F28335 was designed. Taking TMS320F28335 and SST39VF1601 chips as the object, according to the characteristics of DSP external interface and Flash memory, XZCS6 area is used for the external Flash expansion and hardware design, and the operation software of DSP external expansion and Flash memory is designed for erasing, reading, writing, and so on, and the test case is verified. The verification results show that the design has some practical value.