Trains are categorized by speed service In China. Different letters indicate different types of the train, including G, D, C, Z, T and K. The trains numbers with letter G, D or C are high-speed trains.
G-class (for Gaotie, simplified Chinese: 高铁, or "high speed rail") trains are the fastest and newest trains, all with top speeds of 250+ km/h. It even can reach a maximum speed of 380 km/h. For example, train G17 with a maximum speed of 380 km/h finishs the 1385km journey from Beijing to Shanghai in 4h17m.
And the ticket prices of G-class are also the highest