Objective To solve the problem of fast locating primary radiation in dental panoramic tomography apparatus by designing a linear model-based positioning die body. Methods By applying the mathematical principle of solving the linear equation,the two-dimensional plane coordinates were mapped to the detector plane of dental panoramic tomography apparatus, and the horizontal coordinate position was determined by determining the vertical coordinate value through X-ray imaging in the detector plane. Finally, the position of primary radiation in the detector plane was determined. Results The longitudinal characteristics of the image were determined by analyzing the images taken after the application of the model, and the final position of the primary radiation in the detector plane was accurate. By comparing the detection results of die body method and film method, the localization results by the die body method fell within 90% of the image center by the film method. There was no significant difference in the localization results between the two methods by Shapiro-Wilk normality test and paired-samples t test (P > 0.05). Conclusion For narrow-beam devices, the positioning die body designed based on the linear model method can locate the position of the primary radiation in the detector plane quickly and effectively and replace the film method.