Objective To investigate the relationship between the unilateral maxillary sinus fungus ball (UMFB) and maxillary sinus anatomical parameters.Methods The computed tomography (CT) data of 55 patients with UMFB were retrospectively analyzed. The software Mimics 21.0 was used for the three-dimensional reconstruction of bilateral maxillary sinuses. The volume, surface area, gasification coefficient, bone wall thickness, and density of the affected and healthy maxillary sinuses were measured and calculated, and the obtained data were statistically analyzed.Results ①In the UMFB patients, the volume, internal surface area, gasification coefficient, and superior-inferior diameter of the affected side were all smaller than those of the healthy side, and the differences were statistically significant (P<0.05), but there were no significant differences in the left-right diameter and anterior-posterior diameter (P>0.05). The thickness and density of the maxillary sinus bone wall on the affected side were higher than those on the healthy side (P<0.05). ②There were no correlations between the anatomic parameters of the maxillary sinus and the Lund-Mackay score on the affected side of UMFB (P>0.05).Conclusions UMFB is more likely to occur on the side with a smaller volume, surface area, gasification coefficient, and superior-inferior diameter of the maxillary sinus. The increased thickness and density of maxillary sinus bone wall have certain diagnostic value for UMFB.