Abstract: Using the carrier to carry digital information in modern communication is a widespread application, such as PSK and QAM technologies,both of them need the carrier with sin wave. The traditional way to generate carrier uses analog circuit,which is hard to integrate and in bad efficacy. The paper discussed how to use FPGA and DDS to get digital signal generator, which had advantages of small volume and strong functions.The practical application of this digital signal generator in QPSK modulation validated the rationality of this scheme.