With the further development on the Astronomy and navigation of interplanetary spacecraft, the incremental improvements are expected on the VLBI that is real-time, high sensitivity, reliability and more frequency coverage. As one of the main equipments for VLBI station, VLBI data acquisition Rack takes on the tasks of frequency selection, data collection, data encoding, data recording and etc. As the main part of this equipment, Analog Base-Band Converter (Analog BBC) has very complex analog circuits who is poor reliability and very expensive. This paper mainly describes to use the digital integrated circuits to realize corresponding algorithm called Digital Base-band Converter (DBBC) to take place of the analog BBC.The first two chapters of this thesis will introduce the background of this project, the research status in domestic country and abroad, and the new technology on VLBI.In chapter 3, The theory of signal processing on radio interferometry is studied which emphasis on the effects of 3-bit and more than 3-bit quantization, the algorithm of single side-band realization and an operational method to design bandwidth synthesis array.Chapter 4 analyzes the digital sampling which focuses on the under-sampling theory and the quantization effects of ADC (Analog-to-Digital Converter).The DDS (Direct digital synthesizer) is discussed in chapter 5 which gives detail description on how to design, meanwhile, the phase truncation and amplitude quantization error are analyzed.Chapter 6 illustrates the theory of digital filtering which firstly analyzes the characteristic