Objective To establish a method  based on high resolution X-ray computed tomography (HRCT) of the temporal bone for the measurement of anatomical features with round window (RW) as the core, in order to predict the RW accessibility to cochlear implantation (CI).   Methods The preoperative temporal bone HRCT and intraoperative RW accessibility of 60 patients who undergone CI surgery in the Peking University Third Hospital were retrospectively analyzed. Eight anatomical characteristic parameters with RW as the core in CT were measured and compared with the RW accessibility of CI respectively. SPSS 25.0 software was used for statistical analysis.   Results There was no statistical significance in the influence of the angle between the cochlea basal turn (BT) line- middle sagittal line, the cochlea BT line-external auditory canal (EAC) line, the EAC line-middle sagittal line, and the vertical distance between the facial nerve (FN) and the EAC line on the RW accessibility. The angle between the RW-FN connection line and the coronal line passing through the FN, the vertical distance between the RW and the line, the position relation between the extension line parallel to the EAC and the RW, and the position relation between the extension line and the FN on the RW accessibility was statistically significant.  

 Conclusion The difficulty of RW exposure in CI is correlated to smaller angle between the RW-FN connection line and the coronal line passing through the FN, and closer vertical distance between the RW and this coronal line. The RW accessibility can be predicted by the position relation between the extension line parallel to the EAC and the RW and the position relation between the extension line parallel to the EAC and the FN.