Calibration method is a correction method which is frequently used to correct the nonuniformity of infrared focal plane arrays (IRFPA) at present. The algorithm of this method is simple and can be implemented with hardware easily. However, this method also has a shortage of low correction precision. For this, the actual nonlinear response curves of an IRFPA detector is obtained experimentally. Then, the influence of the number and selection of the calibration points on the nonuniformity correction precision of the IRFPA detector is further analyzed. This work has laid the basis for the improvement of the correction precision of the calibration method.