Abstract: With Godson-1processor as the research prototype,a verification method of processor's onchip-debugging function based on JTAG is presented in this paper.The functional coverage model was set up based on on-chip-debugging structure features and the virtual verification prototype was built steadily according to the different memory access modes.The whole verification integrated directed functional test and ISS random test into one flow,and located several ordinarily hard-to-discover bugs effectively. Finally,the functional coverage reached 100%,and the FPGA prototype worked correctly for required long time.