"Thank God it's over because I was so nervous," she said.
"I had a headache this morning. I felt so terrible that I did not know how I would shoot.
"So to win the first gold medal of this Olympics is pretty amazing."
Emmons' win at the the Beijing Shooting Range Hall marks a big improvement on four years ago, where she finished with bronze behind Li and Galkina.
Russian shooter Galkina finished just a point behind the champion to claim silver once more.
Li, who fled the hall in tears, blamed the pressure of competing at home for her failure in the competition saying, "she wasn't fully prepared for the pressure of competing at home".
BBC reporter Eleanor Oldroyd was covering the event and explained: "She’d already talked about the problem of performing in front of her home fans.
"In competitions overseas she wasn’t put off by the chatter of the crowd, because she couldn’t understand what they were saying – but in China, she could."
International Olympic Committee president Jacques Rogge was among the crowd of 5,000 to present the first medals of the Games.
Bookmark with:
What are these?