I have an 8-hour transit in Guangzhou airport, do i need a visa to go out and do some sight-seeing?

Hi, you just need to apply for a free stay permit at the airport providing your passport and flight ticket for leaving.
Metro is most recommended. At the airport, you can take local subway line 3 to get off at Meihuayuan Station. Then walk about 1,200 meters to the Plum Garden of White Cloud Mountain (Baiyun Mountain).