Objective To improve the image quality of magnetic resonance imaging (MRI) in patients with temporomandibular joint disorders. Methods A total of 158 patients with temporomandibular joint disorder were randomized into an intervention group (n=73) and a control group (n=85). Both groups were scanned for temporomandibular joints using superconducting MRI apparatus of T2WI sequences, in the mouth opened position, the self-designed dental occlusion measuring ruler was used for the intervention group to fix the upper and lower incisors, while sterile gauzes were routinely used in the control group. The maximum opening degree, one-time scanning success rate, scanning time and patient comfort before and during scanning were compared between the two groups. Results There was no significant difference in the maximum opening degree before and during scanning in the intervention group (P>0.05), while it was significantly different in the control group (P<0.05). The one-time scanning success rate of the intervention group was significantly higher than that of the control group (97.26% vs. 77.65%), and the scan time of the intervention group was significantly shorter than that of the control group［(364.48±49.43)s vs. (403.93±138.63)s］(P<0.05, P<0.01). There was no significant difference in comfort level between the two groups (P>0.05). Conclusion Application of the self-designed dental occlusion measuring ruler in MRI scan of temporomandibular joint can accurately measure maximum opening degree of patients, effectively fix incisors, improve success rate of one-time scanning and shorten scanning time.