Objective: To investigate the characteristics of magnetic resonance imaging (MRI) of patients with odontogenic sinusitis (OS) and the differences between maxillary sinus fungal ball (MSFB) without calcification. Methods: The MRI of patients suffered OS and MSFB were analyzed retrospectively，who underwent endoscopic sinus surgery (ESS) in our department from January 2019 to May 2021. Ten OS patients and 11 MSFB patients were included. MRI included pre and post contrast T1- weighted (T1WI, TIWI+C), T2-weighted(T2WI) and fat suppressed sequences in multiple planes in both groups were analyzed. Result: MRI of OS patients showed heterogeneous hypointense and isodense signals in T1WI, and show a heterogeneous hyperintense signals in T2WI and fat suppressed sequences. The signal of each wall of maxillary sinus was slightly higher than that of the central region of maxillary sinus. In T1WI+C, the swelling mucosa of maxillary sinus showed "wreath-like" uneven enhancement and papillary like protuberance, while the center is non-strengthening purulent secretion. The mean mucosal thickness of OS was 8.87±6.56 mm, which was significantly higher than that of fungal ball (4.34±3.24mm)(p＜0.05). An hypointense and isodense signal at T1WI and hypointense or signal void at T2WI are characteristic for fungal ball. The collapse with inferior meatus dome in MSFB (90.9% ,10/11) was significantly higher than that of OS (10%,1/10) (p <0.05). Conclusion: The highly edema maxillary sinus mucosal with papillary protuberance and purulent secretion in sinus cavity are characteristic manifestations of OS in MRI. At the same time, the inferior meatus dome is mostly intact and without collapse at the coronal plane through maxillary sinus ostium.