1 of my router has WAN while the other act as a wifi extention because PC is too far away.
I have set both routers' channel as the same, what else is there that I miss? Thanks.

I think one needs to be set up as a bridge. Some routers have that option by default and others don't. I have two Linksys WRT54G routers. One in my room and one in my den connected to the internet. I had to install DD-WRT firmware on the one in my room to get it to act as both a bridge and an access point for my computer, Wii, and XBox. It works great and I can connect devices to it as if it were physically connected to the modem while in reality it is wirelessly attached to the other wireless router. So does your router support the bridging feature by default?

One of the router (TPLink) does not. Which one I should set to bridge? The one that connect to the phone line right? Can my notebook connect to any one of the wifi router?

Usually you have to specifically buy a router that supports WDS or "repeating". An when you do find a device that does it, usually it has some kind of setup that only works with similar models. That isn't always the case, but Ive seen that trend in Dlink and Netgear routers that do support Network bridge, or WDS.

http://www.newegg.com/Product/Product.aspx?Item=N82E16833320025

The ASUS WL-330gE is one such gem that will do everything you probably need. It's tiny, can be powered on USB if needed. You are able to repeat (boost) a wireless signal of your choice for other wireless clients in the area, and connect one device via its single ethernet port. (PC, console, switch, hub) very handy.

If your against purchasing new hardware, you will have to give the name/model and probably firmware version of your current hardware for people to be more help.