The SS8 is an electric express locomotive that was developed based on the two prototypes of the SS5. Like the SS5, it has four axles and 3,600 kW, and the regular top speed has been increased from 140 to 170 km/h. The power is controlled electronically using a thyristor. On June 24, 1998, the number 0001 set a Chinese speed record of 239.6 km/h (148.9 mph). 

The locomotives, which were built in series from 1997, were initially only used on the Jingguang route, which runs from Beijing to Guangzhou. Later, some locomotives were also used on a connection to Hong Kong, where they were initially replaced by type DF4 diesel locomotives due to feared damage to the catenary. Only after the pantographs had been adjusted with the help of the Kowloon–Canton Railway, the SS8 could be used again on this connection.