Abstract: Range gating is a kind of effective method that can eliminate backscattered light and increase the SNR of the range gated laser imaging system. The theory of range gating is described and the key techniques for range gating are analyzed in this paper. On this basis, a few schemes are designed for range gated imaging system such as producing laser pulse by modulated electrical source or mechanical pulsewidth modulator and feasibility of the pulse modulating methods is approved by experiments. Of particular importance, the mechanical modulating method is useful when the light source of active imaging system is CW diode laser. The target image at range of 1 509 m and 675 m is acquired by range gated imaging system. The shortcomings and improvement of these schemes are also presented．