The electricity consumption of the urban metro system can be mainly divided into the following two categories: the electricity consumption for train traction (Et) and the electricity consumption for station operation (Es). Although understanding the hourly fluctuation characteristics of Et and Es contributes to renewable energy integration and achieving carbon emission reduction of the metro system, the hourly fluctuation characteristics have been poorly reported in the literature. Thus, a typical underground non-transfer metro station of a city's metro system in the North China Plain is selected in this study, and Et and Es were monitored to portray their hourly fluctuation characteristics. Results reveal that the hourly Et shows a significant intraday “U” shape on weekdays, indicating two symmetric peaks in morning and evening rush hours. While the hourly Es shows an intraday “flat” shape, indicating it is nearly free from the effect of rush hour. Moreover, it is statistically proved that the train frequency is the core influencing factor resulting in the intraday fluctuation of hourly Et. In the case study, when the train frequency increases from the mean (20 trains per hour) to maximum (32 trains per hour), the hourly Et will increase by 53.4%.