Abstract: The transformation of HermiteGaussian (HG) beams through a complicated optical system with multiple hardedged apertures is studied using Wen's method. A closedform propagation expression is derived which provides the main advantage of the fast algorithm, so that the computational time is great reduced. The propagation of Gaussian beams through such a type of optical system can be regarded as a special case in our theoretical model. Numerical examples of HG beams propagating through multiple aperturelens optical systems by using our formula are given, which show a good consistent with those by straightforward integral of the Collins formula. Further extension of the method and results obtained in this paper is discussed.