The invention provides a method for adjusting an image tube MCP (micro-channel plate) voltage to improve imaging quality of a night vision viewer, aiming at solving the overexposure problem when a UV near infrared digital camera shoots fingerprints on a white background. The method comprises the following steps of step 1, externally connecting two of four lead wires which are connected with an image tube and a high voltage power supply box corresponding to the MCP anode 3 and the MCP cathode 4 with lead wires, so as to perform voltage measurement; step 2, fixing illumination conditions, measuring MCP initial voltage value of the image tube in a dark room or a camera obscura 1, and recording the MCP initial voltage value; step 3, adjusting a knob of a potentiometer 5 corresponding to the high voltage power supply box, measuring the MCP voltage value after the knob is adjusted in real time, and adjusting the voltage of the image tube to a reference voltage value; and step 4, after assembling, identifying whether the camera works normally or not after the voltage is adjusted according to the overall shooting situation of the night vision viewer, if the night vision viewer shoots too slowly, the night vision viewer is judged to abnormally work, thus, the MCP lead wires are externally connected again, and the knob of the potentiometer is adjusted back along a clockwise direction.