In order to realize the analysis of complex wideband electromagnetic signal, this paper introduces a design of GHz wideband IF digital acquisition system based on FPGA, and discusses the design of the hardware and the algorithm of digital signal process. In the system, the signal is sampled by ADC with the speed of 1.6 GHz, and then processed by FPGA. Based on the traditional polyphase filter algorithm improvements, this paper designs the highspeed wideband filter algorithm realized in FPGA. By the way of multichannel parallel processing, this paper designs the highspeed digital quadrature mixing algorithm. The system achieves a maximum of 640 MHz analysis bandwidth and the function of multichannel signal analysis.