Crystal Liu (born August 25, 1987) is a Chinese actress and singer. Although she is often credited as Liu Yi Fei, her legal name is Liu Xi Mei Zi. At the age of 15, Liu Yifei's role as "Wang Yuyan" in the 2003 television serial, Demi-Gods and Semi-Devils propelled her to fame in China.

Born at Tongji Hospital in Wuhan, China, Liu's birthname was An Feng , a 1st Secretary in the Chinese Embassy in France, was a university French Language professor while her mother was a dancer and a stage performer. They divorced when she was 7 years old. After her parents' divorce, Liu lived with her mother, Liu Xiao Li and her name was changed to Liu Xi Mei Zi. She began modelling at the age of 8 and was trained in singing, dancing and the piano. Moving to the United States at 10 with her mother, Liu lived there for four years. In those four years she went to Louis Pasteur Middle School.She returned to China in June 2002 to pursue an acting career and adopted her stage name Liu Yi Fei. In September 2002, she was accepted into the Performance Institute of Beijing Film Academy at the age of 15. She graduated from the Beijing Film Academy in July 2006.

Immediately following her admittance into Beijing Film Academy, Liu received offers to star in various television drama serials. Her first role on television was in The Story of a Noble Family. Shortly after, she was chosen to portray the role of "Wang Yuyan" in Demi-Gods and Semi-Devils, a drama based on the same-titled novel. After 15-year-old Liu Yifei was spotted, she was given the role of "Wang Yuyan" and Liu Tao was cast as "A Zhu".It was this role that established her fame in China. Her fame was further enhanced through her starring role in the 2004 drama series adaptation of the video game, The Legend of Sword and Fairy.

In 2006, Liu starred in another television production based on a book by Jinyong, The Return of the Condor Heroes. She appeared in Jimmy Lin Chih Ying's music video of the song "I Am Still Waiting For You".

In conjunction with her acting career, Liu obtained a recording contract with Sony Music Entertainment Japan in August 2005 and has studied singing and dancing in Japan since then.She released her first single "Mayonaka no Door" with Sony Music on July 19, 2006.

In 2008, she co-starred with Jackie Chan and Jet Li in The Forbidden Kingdom, a martial arts adventure movie in which she played Golden Sparrow, an orphan seeking revenge against her parents' killer. In her quest, she is teamed up with the drunken immortal (played by Jackie Chan) and the silent monk (played by Jet Li).