Based on the discrete Fourier transform and Kogelnik′s one-dimensional coupled-wave theory,the characteristics of the laser beam with arbitrary shapes in both temporal and spatial domains diffracted by reflecting volume grating are analyzed. The intensity distributions of the diffractive laser beam in both temporal and spatial domain are formulated. The diffraction performances of the ultra-short pulsed Gaussian laser beam by reflecting volume grating are specifically simulated. The results show that by increasing the grating′s refractive index modulation or selecting the appropriate grating′s period,the angular spectrum and light spectrum of diffractive bandwidth can be broadened;through enlarging the grating′s thickness,its high diffraction efficiency can be achieved. And in this situation,when the central vector of the ultra-short pulsed Gaussian laser beam satisfies the grating′s Bragg condition,the intensity distributions of the diffractive laser beam both in temporal domain and spatial domain are similar to those of the input laser beam,and the diffraction efficiency is greater than 95%. And the results are instructive for the low-pass spatial filtering of ultra-short pulsed Gaussian laser beam diffracted by reflecting volume grating.