Thank you everyone for useful information.

Now I look at the UA website again and found that the flight schedules have been changed.

UA796: RDU-IAD 6:00am-7:11am (80% on-time)
connection time: 1 hr 2 mins
UA874: IAD-SFO 8:13am-11:19am (70% on-time)
connection time: 1 hr 37 mins
UA853: SFO-NRT 12:56-17:20+1

It means I have more 10 mins at IAD, so I'm considering to try the above flight connection.