According to the practical project application of an infrared imaging system, the basic radiation calibration principle for nonuniformity correction of an Infrared Focal Plane Array (IRFPA) is presented. The mathematic mechanism in which the nonuniformity correction of an IRFPA belongs to function interpolation or fitting is derived. A nonuniformity correction algorithm suitable for project application is given. Meanwhile, to overcome the limitation of device shortages in the practical research work, the simulation technique for nonuniformity correction of an IRFPA is studied in detail and an effective simulation algorithm is given. The simulation technique can meet the validation and evaluation requirements of a nonuniformity correction algorithm in practical projects.