Airport runway capacity estimation is the basis of air traffic flow management. It has tremendous impact on performance of traffic flow management. Therefore, according to the premiss of safe and effective operation of an airport, samples of take-off and touch-down times of aircraft at the runway of Sung Shan domestic airport are collected for the study. Statistical methods are applied to analyze aircraft separations corresponding to the specified flight sequences. The estimated separations are then used to develop a mathematical model. Flight demand and restrictions of the apron are taken into consideration. Reasonable results of the estimated runway capacity are obtained under good weather conditions. Accordingly, decisions regarding the maximum allowable flights can follow this estimation. In addition, this study can be a good resource for the authority to conduct slot management.