Objective To study the relationship between the position of the maxillary sinus floor and the first maxillary molar using cone beam CT, and provide reference for the movement of molars in clinical treatment. Methods A total of 54 patients who underwent orthodontic treatment in our hospital from January 2022 to January 2024 were selected as the research objects. According to the classification of vertical bone surface type, they were divided into average-angle group, high-angle group and lowangle group, with 18 patients in each group. Cone beam CT was used to measure the distance between the maxillary first molar and the maxillary sinus in each group. The classification of the relationship between the root tip of the maxillary first molar and the maxillary sinus floor and the distance from the maxillary first molar to the maxillary sinus floor were compared among the three groups. Results There were statistically significant differences in the classification data of the relationship between the root tip of the maxillary first molar and the maxillary sinus floor among the three groups (P <0.05). The proportion of 1+2+3 in the high-angle group was higher than that in the average-angle group and the low-angle group, but the difference was not statistically significant (P >0.05). The proportion of 1+2+3 in the average-angle group and the low-angle group were consistent. The distance from the mesiobuccal root, distal buccal root and palatal root of the first molar to the maxillary sinus floor in the high-angle group was better than that in the average-angle group and the low-angle group (P <0.05). Conclusion Through CBCT examination, it can be found that the position of maxillary sinus floor in patients with high angle is low, which is adjacent to the root of maxillary first molar, and the root tip of maxillary first molar is mostly in contact with the maxillary sinus floor.