Abstract: The losses Bessel-Gaussian beams, a kind of non-diffracting beam, propagating through a hard aperture are studied, and ageneral formula is derived. As an example of applications, numerical calculation is performed to calculate the losses of Bessel-Gaussian beams propagating through a circular aperture. The obtained results are analyzed and discussed. The proposed method can also be applied to calculation of the losses of other types of laser beams propagating through a hard-edge aperture.