Two-time winner Baun (right), who has beaten the world champion five times in 11 previous meetings, eventually fell 19-21, 25-23, 21-9, in 65 minutes.
Despite her narrow escape, which included facing match point, Wang Yihan kept calm and never once lose her focus as she showed just why she is the favourite for the gold medal at the London Olympics later this year.
“Overall, I was quite relaxed and was not too tired,” said Wang Yihan, who won this tournament in 2009.
“I could see that she was tired in the third game and was able to close out the match. I have some strapping on my thigh, but it is not serious.
“There, however, was one moment when I was going towards the net and slipped. I was a bit worried at that stage.
“I haven’t thought about winning the title again. I still have to face my teammate in the semi-finals first.
“I want give a good performance first before thinking about winning any championship.”
Wang Yihan will meet teammate and defending champion Wang Shixian for a place in the final after the latter defeated Jiang Yanjiao 21-18, 21-10.
The other semi-final will see Taipei teenager Tai Tzu Ying taking on German Open champion Li Xuerui.
In the mixed doubles, unseeded Malaysians Chan Peng Soon-Goh Liu Ying (left), go in search of their first OSIM BWF World Superseries Premier title when they reached the semi-finals by beating English-Scottish combination of Chris Adcok-Imogen Bankier 21-16, 15-21, 21-17.
Peng Soon-Liu Ying will meet fourth seeds Tontowi Ahmad-Liliyana Natsir in the semi-finals after the Indonesians survived an encounter with English duo Nathan Robertson-Jenny Wallwork, winning 21-19, 14-21, 21-6, in 59 minutes.
World champions Wang Xiaoli-Yu Yang and second seeds Tian Qing-Zhao Yunlei also made it to the women’s doubles semi-finals.
For full results, click here.