Abstract: A detector correction method in grating-based X-ray phase contrast imaging (GBPCI) was proposed in this paper. This method does not require to remove the source grating which is close to X-ray source, and considers the source grating and X-ray source as a unity in the gain correction. On the GBPCI setup based on geometric projection theory, the comparison experiment between the previous and the proposed detector correction method was performed, and the two methods obtained the same results. The experimental results show that the proposed method greatly simplifies the experimental operation and improves the stability of the system, which is of great significance for the clinical application of X-ray phase-contrast imaging.