Objective To investigate the correlation between the orthodontic pain score and occlusal function at 24 h after the first time treatment in the patients with fixed orthodontics.Methods Seventy-eight voluntary subjects were selected and treated with MBT straight wire correcting appliance.The VAS scores of spontaneous odontalgia and biting odontalgia (SO-VAS and BOVAS),masticatory efficiency (ME),masticatory times (MT),maximal occlusal force(MF)and occlusion rate before wearing the fixed appliance(T0),at 24 h after wearing(T1) were measured.The changes of above indicators were observed and the correlation among indicators was investigated:Results (1) BO-VAS and SO-VAS were increased after 24 h of orthodontic treatment,while BO VAS was (59.49 ± 19.06) mm,which was significantly higher than SO-VAS[(23.21± 20.80) mm].After 24 h of fixed orthodontic treatment,the patients had occlusal dysfunction,which manifested by ME,MT,MF and SO decrease compared with T0 (P＜0.05).(2) BO-VAS was negatively correlated with ME,MT and MF (P＜0.05).There was no correlation between SO-VAS and occlusal dysfunction.Conclusion There is no obvious magnitude correspondence relation between the occlusal dysfunction grade and the pain grade on the first day after fixed orthodontic treatment,the VAS grading is not yet fully representative of the occlusal dysfunction level,but the credibility of BO-V.AS score is higher than that of SO-VAS score in assessing the degree of occlusal dysfunction.