*yuhong@siom.ac.cn

Ultrafast x-ray diffraction imaging provides an opportunity to realize x-ray nanoimaging of biomolecules before radiation damage, while the image resolution is still restricted by the photon flux. Fourier-transform ghost imaging based on the temporal intensity correlation can achieve diffraction-limited imaging. However, a large number of temporal samplings are inevitable, which makes it almost impossible to be implemented in the ultrafast x-ray imaging. Here, we propose an x-ray single-exposure Fourier-transform ghost imaging (SFGI) approach. The Fourier information of an unknown sample can be obtained by measuring the spatial intensity correlation between two speckle fields, and the sample needs to be exposed only once. In our demonstration experiment of SFGI, the Fourier-transform diffraction pattern of a two-dimensional sample is achieved, and its face-centered-cubic feature in the spatial domain is retrieved successfully. The simulation results of the DNA origami and rice dwarf virus indicate that a spatial resolution of 10 nm may be reached, and x-ray ghost imaging with 0.1 photon/pixel speckle detection can be expected. Our research paves the way for the future application of ultrafast x-ray ghost imaging.