Abstract: Railway transportation is one of the major industries affecting the national economy and people's livelihood. In order to determine the optimal price of railway freight transportation on the premise that the service levels of customers were guaranteed. Firstly, based on the actual situation of life, the reasonable assumption was made and a quantitative description of cost and reliability were given, then,the total cost was used as the objective function. the capacity was used as the decision variable, the pre-set reliability was used as the constraint condition to make sure the optimization model was established and the optimal solution was obtained, finally, the calibration parameters were analyzed by examples, and the influence of parameters on the optimal capacity and the optimal price was discussed. The results show that the model established can clearly reflect the trend of the optimal solution with the variation of various parameters, which can better reflect the industry characteristics of the monopolistic industry and obtain concise and basically reasonable results.

Key words: monopoly, optimization model, optimal price, optimal capacity, optimal marginal cost