Testbench for satellite communication terminals is required to be more universal since satellite communication systems are becoming multi-band and multi-system integrated. General-Purpose-Processor based Software Defined Radio(GPP-SDR) is suitable to solve this problem yet the high-speed data transmission between the processor and RF front-end of GPP-SDR is still one of the main bottlenecks. In this paper, to satisfy the requirements of satellite communication terminals testing, a high-speed transmission method based on interrupt mechanism is proposed. The real-time of the transmission interface is also optimized by utilizing the Xenomai Operating System(OS). A series of experiments are designed to test the actual transmission data rate, interrupt loss probability and other indexes, verifying that the proposed approach has good performance in high speed and low latency and can meet the current requirements on universal testing of satellite communication terminals.