According to the International Energy Agency (IEA), China’s rail system will become fully electrified by 2050. However, in some remote areas with a weak power grid connection, the promise of an electrified railway will be hard to achieve. By replacing conventional fuels with clean and environmentally-friendly energy, overall carbon emissions would be significantly reduced, contributing to the fulfillment of the carbon-neutral commitment. This study reviews clean energy exploitation in the railway transportation system and the distribution of renewable energy sources along the railway lines of China. The evaluation results show that China has huge energy potential. In terms of photovoltaics alone, the annual power generation of China’s high-speed railway is about 170 TWh, meaning that the energy self-consistency rate for high-speed railway can reach 284.84%. Efficient exploitation of clean energy sources for China’s railway transportation system would effectively mitigate anxieties surrounding energy shortages.