The invention belongs to the technical field of display panel defect detection, and discloses a fast auto-focusing method based on a display panel. The method includes the following steps: a focusingscreen image of a display panel is collected, focusing is carried out by dichotomy in the full focal range, the clear focusing range of the image is determined by long-step focusing, and the clear focusing position is determined in the focusing range by short-step focusing; an image corresponding to the clear focusing position is collected at the clear focusing position, and the focusing clarity is judged; if the focusing clarity satisfies a preset threshold requirement, the image is output; and otherwise, an image is collected and the focusing clarity is judged again after auto-focusing fine-tuning until the focusing clarity satisfies the preset threshold requirement, and the image is output. According to the auto-focusing method provided by the invention, the clear focusing position is calculated through coarse focusing, and fine-tuning is carried out according to the clarity of the image at the focusing position. Therefore, the focusing accuracy is improved, error focusing is prevented, the accuracy of defect detection is improved, and the detection time is shortened.