Large-format full-frame transfer charge-coupled devices(CCDs)feature large array sizes，and their output images typically contain defective pixels. In addition，the brighter-fatter effect exists widely in CCD detectors. Both factors affect the temporal variance and gray-scale mean calculated from image data，resulting in inaccurate measurement of the devices’photon transfer curve and a significant reduction in the accuracy of device parameter estimation. To improve the accuracy of evaluating the photon transfer curve nonlinearity for large-format full-frame transfer CCD detectors， this study investigated image processing and correction methods. By partitioning，merging image data，and eliminating defective pixels，the problem of reduced temporal variance of images caused by defective pixels was corrected，the correlation between adjacent pixels induced by the brighter-fatter effect was reduced，and the accuracy of evaluating the photon transfer curve nonlinearity and multi-channel gain of the device was improved. The results show that the photon transfer nonlinearity of the device was improved by an average of 97%，and the gains of all channels of the same device were corrected to a common range after image processing. The proposed algorithm enhanced the measurement accuracy and efficiency of large-format full-frame transfer CCDs，which has significant practical value and may guide future research on detectors used in ultra-high-resolution scientific instruments.