The most optimal variant to get from Guangzhou to Shanghai is, of course, air travel, there are a lot of flights, the flight takes a bit more than 2 hours. For example, if you use the services of Air China, then at 7:30 in the morning, at 9:40 you will be there. If you prefer European companies, you can use the services of KLM. You can also take advantage of the train service, a high-speed train overcomes the distance from Guangzhou to Shanghai in 16 hours