Objective To investigate the clinical effect of modified tapping screw assisted orthodontic traction in the treatment of impacted mandibular premolars.Methods 50 cases of low impacted premolars were treated with modified tapping screw,double retention by thread machine and adhesive,and orthodontic traction.Results All the 50 cases of low impacted teeth were pulled to the normal position,there was no significant difference in pulp vitality and root length between the two groups at 1,3 and 6 months after active orthodontic treatment.Conclusion Modified screw assisted orthodontic traction in the treatment of low impacted premolars has reliable retention force,small surgical window,and a greater clinical value.