Abstract: 【Abstract】 Objective: To investigate the soft tissue changes and the relationship with the hard tissue in the class III malocclusion adult patients treated with premolar extraction. Methods: Thirty-four adult patients with skeletal class III malocclusion who met the including criteria were included into this retrospective study. Lateral cephalographs of pre and post treatment were traced.Relevant measurements of pre and post treatment were analyzed. Results: After orthodontic treatment，the values of U1-SN（°） was descreased 5.22°, the values of L1-MP（°）was descreased 13.86°，the angle of MP/FH was increased 1.78°averagely.The SL line as a reference，the retraction of upper incisor was 2.41mm，the retraction of lower incisors was 6.49mm significantly；the retraction of upper lips was 1.34mm，the retraction of lower lips was 3.82mm，the values of Ns-Sn-Pos was increased 3.36°, the values of H angle was descreased 2.96°，after orthodontic treatment（P＜0.05 or P＜0.01）. Relevant measurements of chin were non-significanty. The retraction of upper incisor was the only measurement positively correlated with upper lip retraction. The retraction of upper incisor and lower incisor were correlated with the lower lip retraction；the upper lip retraction was correlated with lower lip retraction. Conclusions：Soft tissue profile improved significantly after four premolars extraction.The changes of soft tissue profile was moderate correlated with hard tissue.

Key words: skeletal class III, malocclusion Orthodontic, extraction treatment, soft tissue profile