This paper presents the design and realization of a large capacity airborne waveform recorder for UWB (ultra wide band) system based on FPGA and Flash array. The system has 80 MT29F64G08AJABA NAND Flash Memory chips and provides a total 640GB storage capacity. With ADC working at 100MHz, the storage time can be more than 100 minutes. For offline data analysis, the system provides a Gigabit interface to PC, and the data rate can reach 25MB/s. This device also can be applied in other measurement instruments and systems. The system structure, implementation and test results are described in detail.