Abstract: In order to provide the basis for parameter selection of vocal diseases classification, a nonlinear dynamic modeling method is proposed. A biomechanical model of vocal cord with polyps and paralysis is introduced, which coupled to glottal airflow to produce laryngeal sound source. And then the fundamental frequency and its perturbation parameters are solved. Poincare section and bifurcation diagrams are applied to nonlinear analysis of model vibration. The relationship between pathological parameters with different sub-glottal pressure and the flmdamental frequency included Lyapunov exponents are analyzed. The results show that, vocal cord paralysis reduces the fundamental fre- quency, in which the chaos occurs only within a certain pressure range; while vocal cord with polyps don't reduces the fundamental frequency, in which the chaos is distributed throughout the entire range. Therefore this study is helpful for classification of polyps and paralysis by the acoustic diagnoses.