Objective To study the effects of the size and diffraction of tympanic membrane perforation on hearing system of human ear. Method The whole temporal bone from a healthy volunteer is scanned using spiral CT. The digitized outlines of images are imported into ANSYS to construct a three dimensional finite element model of the human ear. ResultsThe resonance frequencies become 3.6, 4.4 and 4.6 kHz with the increase of perforation areas as 0.97, 3.66 and 7.97 mm2, respectively. The larger perforation in the tympanic membrane results in a lower stapes footplate displacement. The displacement swing of the stapes footplate decreased clearly under the action of sound wave from the diffraction. The peak values of the displacement nephogram of the tympanic membrane are 0.32, 0.20 and 0.19 μm at 1000 Hz, respectively. At the resonance frequency, the peak values of the displacement nephogram of the tympanic membrane are 0.20, 0.14 and 0.09 μm, respectively. Conclusions The larger the size of the perforation is, the smaller stapes footplate displacement will be, especially at the lower frequency of 4 kHz with the higher resonance frequency. The peak values of displacement nephogram will become smaller with the increased size of perforations. The results would give helpful information for the clinical treatment.