Abstract: The satellite navigation signal simulator is an important tool for the research and development of user terminal equipment and verification of satellite navigation signal system, which provides input signal source for the design, verification and testing of user terminal equipment. The accuracy and channel consistency of the signals generated by the early RF synthesis technology are poor. The subsequent analog IF synthesis techniques have the problem of channel-to-channel skew. While the commonly used digital IF synthesis techniques will introduce phase jitter problems. Therefore, based on the software defined radio(SDR) architecture of PXI Express (PXIe) bus, this paper designs and implements a software and hardware combination simulator using digital baseband synthesis technology. LABVIEW graphical programming language, simple and high efficiency, is adopted to develop mathematics simulation software in the host computer, and the software finally generates synthesized digital baseband signals. The modular virtual instruments of national instruments(NI) are utilized to receive and deal with the synthesized digital baseband signal generated by the host computer, and then generate global positioning system(GPS) RF signals that can be received by user terminal equipment. The simulated GPS signal is verified to be correct by utilizing spectrum analyzer to analyze the frequency and bandwidth of simulator output signal. And also it verified to be accurate and effective by utilizing commercial receiver to figure out the position and to analyze the signal quality, positioning results and positioning error in static and dynamic scenes.