Railroad line capacity is influenced by Quantitative and Qualitative factors which is applied by parameter to calculate it. But these parameters have been used experiential value without analyzing its reasonability or appropriate level. In this paper, we introduce the concept of robustness to Quantify parameter and evaluate robustness of it. For this purpose, we develop parameter evaluation simulator and present it. If this simulator is utilized, we can find the parameter having appropriate robustness and it will be applied to calculate more reasonable and systematic railroad line capacity.