Base on the fact that a hard-edge aperture function can be expanded into a finite sum of comp lex Gaussian functions, the app roximate analytical exp ressions for the propagation characters of Hermite-Guassian beams passing through double rectangular apertured are derived.The approximate analysis uses Collins formula . At last, Matlab il-lustrates some numerical examples. It is shows that the propagation characters of Hermite-Guassian beams are closelyrelated to the beam parameters,optical system parameters, the size of apertures and the interval of apertures. The results can be straight forwardly used in other apertures and other beams, also is app lied to controlling beams and designing optical systems.