Range gating is a kind of effective method which can eliminate backscattered light and increase the SNR of the laser range gated (LRG) imaging system. The theory of range gating is described ,based on which ,the key tech2 niques for range gating are analyzed briefly. The shortcomings of the traditional range2gated synchronization control system is pointed out . An improved LRG imaging system is proposed. The key research tasks which LRG imaging system need to focus on are discussed. The development trends of range2gated active imaging are predicted.