Abstract: Due to the limitation of space resources and geographical location, the design of closed spaced parallel runways has become one of the most direct ways to increase the capacity of airports at present. Although the capacity has been improved compared with the single runway operation, it retains a higher safety margin because of its isolated operation mode, which leads to the low utilization rate of parallel double runways and the unknown effect of capacity improvement. The capacity needs to be evaluated in advance at the pre-research and design stage to obtain the airport design with optimal performance. Now the mature software for the operational efficiency evaluation of civil airports on the market is mainly foreign software vendors, and the self-developed tools are scarce, which makes it difficult to conduct the most intuitive evaluation of the design by quantitative means at the early stage of design. Therefore, based on the design layout of standard close-range parallel double runways, this paper applies computer simulation technology to carry out mathematical modeling and system logic simulation for the whole flight process. What's more, this paper builds the technical path of runway capacity simulation and evaluation for single and double runways to realize the development of real-time capacity calculation prototype system, which can adjust parameters freely for the approach and departure of closed spaced parallel runways, accomplishes capacity simulation for different staggered distance design parameters, and assists in the best design decision and result evaluation.