Objective To study effects of the bacterial biofilm at different growth stages on dynamic behavior of the titanium partial ossicular replacement prosthesis (PORP), so as to provide theoretical references for clinical treatment of diseases such as secretory otitis media. Methods Based on the CT scan images of normal human right ear and combined with the self compiling program, a 3D finite element model of the ear was reconstructed for dynamic analysis on sound conduction, and compared with the experimental data. The model was computed by harmonic response analysis method, and the sound conduction effect of bacterial biofilm grown on PORP at different growth stages was analyzed. Results The simulated amplitude of umbo and stapes footplate was in accordance with experimental measurements, which confirmed the validity of this numerical model. The existence of biofilm would cause 0-1.6 dB hearing loss at low frequencies. The growth of biofilm in the radial direction of PORP would cause 0-12 dB hearing loss at intermediate and high frequencies, especially at 8 kHz, and the hearing loss could be as high as 11.2 dB. Conclusions The bacterial biofilm has an impact on hearing by reducing the hearing at low frequencies while raising a little at high frequencies. The biofilm grown in the radial direction of PORP will reduce hearing, and affect the working efficiency of PORP on hearing restoration.