Objective Aiming at solving the problem of the middle-aged and old women suffering from stress urinary incontinence (SUI), which can seriously affect their physical and mental health, the numerical study on urodynamics in pelvic floor of the female urinary system is conducted. Methods According to the characteristics of interaction coupled between urine and pelvic organizations, the SUI urine dynamics model was established based on computational fluid dynamics. Thus, the stress, strain and displacement of the urine system, and the pressure or velocity distributions in the urine flow, were analyzed. Results The stress, strain and displacement of elastic structure in the urinary system fluctuated with time，which played the important role in the mechanical mechanism of SUI. Conclusions It is not only necessary but also available to apply the fluid-structure interaction model to study the urinary system of SUI, and the urodynamic simulations can provide the theoretical foundation and technological method for the prediction and assessment of SUI diseases in clinic.