Single-photon-counting imaging technology has been widely used in ultraweak bioluminescence, space environment detection and nuclear radiation detection. The structure and working principle of an ultraviolet single photon imaging system based on the microchannel plates and the wedge and strip anode are introduced. The gain characteristic of dark count of two and three microchannel plates is investigated under different voltages respectively. The experimental and fitted results show that the dark count pulse height distribution of microchannel plate has exponential distribution, and the dark count rate rises as the voltage increases. It is shown that the gain becomes more homogeneous as the voltage increases by measuring the pulse height distribution under different voltages. Then the effects of microchannel plate voltage and distance on system resolution with two microchannel plates are tested. It is revealed that the system resolution rises as the voltage of microchannel plate increases, and can be improved also by increasing the distance of microchannel plate properly.