The invention relates to a method for extracting panoramic image from three-dimensional conical beam CT data of a dentistry department, and the method comprises the following steps: (1), generating a dental arch curve according to the three-dimensional conical beam CT data of the dentistry department; (2), extracting a three-dimensional oral cavity panoramic curved surface according to the generated dental arch curve; (3), expanding the three-dimensional oral cavity panoramic curved surface and obtaining an oral cavity panoramic image. The method can extract a tooth curved surface faultage image through the three-dimensional CT data, solves problems of structure overlapping and image fuzzy, and improves the diagnosis precision. The method can obtain a single-frame oral cavity panoramic image, and the single-frame oral cavity panoramic image can display all teeth. The method can clearly recognize the anatomical structure of teeth, such as enamel, dentin and dental pulp, effectively avoids image fuzzy caused by perspective, and has no structure overlapping.