Resolution is one of the important parameters of image intensifiers, which reflects the target detection performance (including the night working distance and the image definition) of the combined night vision instruments in 0.001 lx to 0.1 lx dark environment. At present, the mainstream measurement method of this index in the industry is subjective evaluation. In addition, several feasible and reasonable objective evaluation technologies have been presented in recent years. Such as, the objective evaluation method of low-light-level image intensifier resolution based on FFT. However, the disadvantages of traditional subjective evaluation methods are strong human uncertainty and low accuracy, while the traditional objective evaluation techniqes face the challenges of improving time effciency and reducing artificial intervention. To solve the problems above, an objective evaluation method of the resolution of image intensifier based on the gray variation features of the stitched stripe unit image is proposed. The main idea of the method is to scan the stitched unit image with the fixed size template, and calculate the unit definition according to the obtained gray change sequence. The general step of the method is to rotate the target image to the appropriate direction, and then extract the resolution image from the target image by using the spatial position relationship between the image block and the central box of the diaphragm. Then, the cropped resolution image is rotated to a correct direction by means of the image information, and the independent unit image is extracted from the resolution image by using the spatial position correspondence relationship of each stripe unit. The adjacent sequential images belonging to the same unit are stitched along the stripe direction in order, and a fixed-size kernel is used to scan the stitched stripe unit image along the stripe change direction to generate the definition of stripe unit. Finally, the resolution of image intensifier is estimated by combining the constructed definition-resolution correspondence of the stripe unit with the linear fitting algorithm. In order to verify the performance of this method, it is compared with the traditional evaluation method, including the traditional subjective method and the traditional objective method. Besides, six image tubes with different resolutions are adopted in the experiments. Among them, the comparative experiments of timeliness and accuracy shows that, the proposed method is superior to the traditional objective method in timeliness and evaluation accuracy, and better than the traditional subjective method in test accuracy. In addition, the repeatability of the method is also investigated, and the traditional subjective evaluation method is used as the comparison. The results show that for the image tubes with a resolution higher than 40.3 lp/mm, the subjective evaluation results varies greatly, and for the image tubes with a resolution lower than 35.9 lp/mm, the objective evaluaiton results fluctuate greatly, but the repeatability of the proposed method is stronger on the whole. To sum up, the proposed objective evaluation method can overcome the disadvantages of traditional method, which provide an effective and feasible scheme for the standardized measurement of this parameter.