Objective To investigate the negative effect of cigaratte smoking on periodontal theraphy. Mothods 84 patients with periodontopathy were selected and divided into two groups. The smoking group (group A) included 33 patients and the non-smoking group (group B) included 51 patients. All the patients received a systematic treatment. The effects of the treatment between different groups were compared through the debris index(DI),calculus index(CI),periodotal disease index(PDI) which were respectively recorded before and after treatment.Results After the treatment the DI,CI,PDI of two groups were all decreased; wheras compared with group A, every index of group B was significantly lower. Conclusions Somking seriously influences the effect of periodontal therapy. Therefore, to give up smoking is very important for preventing and treating periodontopathy.