According to the second-order moment of nonparaxial scalar beam based on the accurate definition of light intensity, the beam waists, far-field divergence angles and quality factors of truncated nonparaxial scalar Gaussian beams under different waists and diaphragm apertures were calculated, and the parameters were compared with the counterpart ones of free Gaussian beams and planar waves diffracted by small circular aperture. Numerical calculation results show that truncation parameter, which is defined by the ratio of aperture radius to beam waist, plays an important role in the propagation characteristics of truncated Gaussian beams. Truncated nonparaxial scalar Gaussian beams follow the same propagation laws of free Gaussian beams when R/ω0>2 which implies that the influence of diaphragm aperture can be ignored when diaphragm aperture is twice of waist for nonparaxial scalar Gaussian beams defined by accurate definition of light intensity. Meanwhile, truncated nonparaxial scalar Gaussian beams tend to truncated planar waves when R/ω0<0.3. This means that Gaussian beams can be treated as planar waves when aperture radius is 0.3 times of beam waist. When truncation parameter is between 0.3 and 2, both the effects of waists and diaphragm apertures should be taken into account.