Abstract: The direct numerical integration,the complex-Gaussian-function expansion,the matrix approach and the beam mode expansion used to simulate beam propagation through optical systems containing hard-edged apertures are compared. It is shown that the direct numerical integration is a widely applicable method,but is very cumbersome and time-consuming as the number of ape rtures increases. The complex-Gaussian-function expansion provides a useful method for fast simulating the hard-edged diffracted beam propagation in the Fresnel and Fraunhofer regions,and obvious calculation errors exist only in the extreme near field. The matrix representation is applicable to the hard-edged diffracted beam propagation in both Fresnel and Fraunhofer regions,but holds only for rotationally symmetrical optical systems and beams. The beam expansion method is suited to approximate the weakly truncated beams in the far field.