According to the in-orbit calibration requirement of a spaceborne infrared imaging system, an online nonuniformity calibration and real-time correction chip system is developed for Infrared Focal Plane Arrays (IRFPA). The system is based on a Field-Programmable Gate Array (FPGA). Because the design of its input signal is standardized, it can be used for on-line nonuniformity calibration and real-time correction of IRFPAs for various infrared imaging systems. Driven by a clock signal, the system operates in a pipeline way. It can acquire calibration images and update the correction coefficient in memory on line while correcting the nonuniform images in real time. It has the advantages of small volume, fast operation, stability, reliability and easy updating. This work has opened up an effective way for the in-orbit nonuniformity calibration of IRFPAs used in spaceborne infrared imaging systems.