Abstract: To meet the requirements of high speed data transmission, multi-level modulation and the system flexibility in space applications, a modulation system design scheme was introduced, which has adopted the new techniques of the FPGA and DAC based communication system, and can be used for high speed data transmission with QPSK, 8 PSK, QAM or other kinds of digital modulation. The difficulties such as the high speed based-band signal conversion, wide-band modulation, carrier suppression, high frequency and high precision clock generation in the design and implementation of this modulation system are analyzed, and the solutions are also given. The test result shows that this modulation system can satisfy the performance requirements for most space applications. When the carrier frequency is 2 GHz, the transfer data rate of this modulation system with 8PSK modulation is up to 750 Mbit/s, while the EVM (Error Vector Magnitude) of the modulated signal is only 3.3 %.