The detailed core structures of misfit dislocations in the AlSb/GaAs（001） heterostructure system were studied by 200 kV LaB6 filament high-resolution electron microscope. In combination with image deconvolution, the［110］ images were transformed into the projected structure maps, and the image resolution was enhanced up to the information limit of the microscope. To distinguish Al and Sb atoms in the AlSb film, the image contrast change with the sample thickness was analyzed for the perfect region in deconvoluted image, and the positions of Al and Sb atoms in the dumbbells were determined based on the image contrast theory of the pseudo-weak-phase object approximation. Then the structure models of two types of misfit dislocations were constructed. As the simulated images are in good agreement with the experimental images, the AlAs type interface and the core structures of obtained Lomer and 60° misfit dislocations were determined.