To study the expression and relationship of Pin1 and CyclinD1 in adult papilloma of larynx, and the effect of both in laryngeal papilloma's canceration.Ninety-two cases of paraffin section with immunoperoxidase (SP) staining method was used to detect the distribution of Pin1 and CyclinD1 in 10 cases of laryngeal normal epithelial tissue, 39 cases of laryngeal papilloma, 27 cases of laryngeal papilloma with middle, severe atypical hyperplasia and 16 cases of laryngeal carcinoma.The distribution of Pin1 and CyclinD1 increased gradually from laryngeal normal epithelial tissue to laryngeal carcinoma (P0.0125), but there had significant difference of the expression of Pin1 and CyclinD1 among the rest groups; There was significantly direct correlation between the expression of Pin1 and CyclinD1 (P<0.05).The hyper-expressions of Pin1 and CyclinD1 may play a key role in laryngeal papilloma's malignant change. Pin1 up-regulating the expressions of cyclinD1 possibly participate in its malignant change.