The load of railway traction substations fluctuates because accelerating timing of each train is different. Therefore it is difficult to predict the amount of the load properly. In such a background, the past research published the correlation equation between hourly instantaneous maximum power and the amount of feeding power. This correlation equation is still referred to determine the capacity of the rectifier in traction substations. However, this correlation equation is based on the load in 1954 and it is suspicious that this correlation is suitable to present load. In this research, the authors collected data of present electric rolling stock load and verified the conventional correlation equation. As a result, it has been found that the conventional correlation did not hold for the present load and it is needed to be revised. In addition, the authors have examined the applicability for the railway lines we can not use the data of load by using simulation.