In the production and propagation of lasers there are more or less limiting apertures. There- fore, the beam propagation through hard-edged apertured optical systems is of practical importance, and a variety of simulation methods have been developed. As usual, the direct numerical integration of the Collins formula provides an exact simulation method, but it becomes very cumbersome and time consumi-ng as the number of apertures increases. In this paper four concise methods, i.e., the analytical propa- gation equation, recurrence algorithm, complex Gaussian function expansion and matrix representation have been used to simulate hard-edged diffracted beams. Their advantages and applicable range are analyzed and some improvements are discussed.