It took me about 4 hours to get it rooted. The reason why I have to root LG Optimus One is that the apps came with the phone always remind me the updates. But, there is no enough internal storage room for them. I can not even delete them. To disable or delete the apps, I have to do the Root first.
OK, above is the background. Now I put the helpful records for reference, some one may need it.
It is LG Optimus One P500h. With Telus.
The tool is Super One Click 2.3.3. Download here.