The flat panel detector is a key component of cone-beam CT, and the signal crosstalk between pixels is the main factor that causes the spatial resolution of the projection image to be lowerthan the possible highest resolution of the flat panel detector. It is essential to correct the signal crosstalk of the flat panel detector forimproving the detection accuracy of cone-beam CT. In this article, the crosstalk correction effect of the point spread function matrices with different accuracy, the relationship between the point spread function and line spread function, and the similarity between the relationship and X-ray imaging are studied, based on the signal crosstalk correction idea of the point spread function matrix deconvoluting projection image. In addition, a new method for calculating the point spread function matrix of a flat panel detector is proposed,which combines the knife edge method for measuring line spread function with parallel-beam CT scanning reconstruction. In DR/CTscanning experiments, the spatial resolution of DR projection image is improved from about 10 lp/mm to better than 25 lp/mm and thespatial resolution of high-energy CT image is improved from less than 4 lp/mm to better than 5 lp/mm after correcting signal crosstalk by the proposed method. Experimental results show that the proposed method can effectively correct the signal crosstalk of flat panel detector and improve the spatial resolution and contrast of cone-beam CT images.