The utility model relates to a field, the utility model provides a FFT that can dynamicly dispose adds window device based on FPGA, in order to reduce the influence that the frequency spectrum leaked, the device includes FPGA and window function generation module, FPGA includes the ROM unit, DSP multiplication unit, address count state machine, window function generation module and ROM unit connection, the ROM unit is connected with address count state machine, the input and the ROM unit connection of DSP multiplication unit, the IQ data of window are waited to add in another input of DSP multiplication unit. The utility model provides an adding the window device and having realized that FFT adds the window, the window function type can dynamicly dispose with counting, has more that the efficient adds the window performance, and the device can work under the high frequency clock in addition, has higher stability and reliability and relatively low consumption, very big reduction the influence that brings of FFT frequency spectrum leakage.