I'm going to have a stopover for about 2 hours in Guangzhou, from lax to manila.do I need a visa?

you do not need a visa , if you have the interline tickets , you can stay there for at most 72 hours without visa .
but as you only have 2 hours so i suggest you stay in the airport .as the airport is far from downtown . 2 hours is not enough for you to make a round trip .