Aiming at the online upgrade demand of field programmable gate array (FPGA) in the hardware design architecture of "Longxin processor+FPGA", we design an IP core that can realize the online upgrade of FPGA program through LIO interface. Design the LIO interface slave module to realize the conversion of LIO interface read/write operation; design the online upgrade operation instruction and protocol processing module, so that the IP core can realize the processing of complex data through the simple interface; design the state information control module, so that the Longxin processor can realize the effective read/write operation of the IP core by querying the corresponding registers; and put the designed online upgrade IP core in the national miniature model number of SMQ7K325T. The designed online upgrade IP core is put on the FPGA of SMQ7K325TFFG900 for practical verification. The results show that the IP core can complete the FPGA program online upgrade, and the performance is stable.