Sun first entered show Business by participating in 2001's Star Search, held by Singapore's MediaCorp. She reached the finals and earned the praise of judge Andy Lau. Following the competition, Sun joined Hairun Media as their first flagship Artist.

In 2003, author and TV Producer Hai Yan selected her for the female lead in the television series Goddess of Mercy. Sun received overwhelmingly positive feedback from audiences for her portrayal of An Xin, and rose to fame in China as one of the most promising young actresses. In an interview with Global Times, Sun thanked Ding Hei, the Director of Goddess of Mercy saying; "Not only because he provided me with [the role of] An Xin, but what's more, he believed in me, a person who never received any formal acting lessons. ... It benefited me all my life."

In 2006, Sun won the Best Newcomer award at the 28th Hundred Flowers Awards for her performance in Huo Yuanjia co-starring Jet Li. She then starred alongside Huang Xiaoming in Shanghai Bund (2007), a mainland remake of the 1980 television series The Bund.

Sun starred in Gordon Chan's horror-adventure film Painted Skin (2008), and was nominated for the Best Supporting Actress award for her performance as a young and inexperienced demon hunter at numerous award ceremonies. The same year, she starred in Gao Xixi's military-romance drama Tian Mi Mi. The series was chosen by the Chinese Radio & Television Association as one of the Top Ten television series of the year.

Sun then starred in Iron Road (2009), the second joint venture created under Canada/China co-production treaty established in the 1960s. She plays a poor Chinese girl in search of her father who works at a railroad in North America, and challenged speaking in English for the film. For her performance, Sun was crowned Best Actress at the 2nd Roma FictionFest and the 25th Gemini Awards. The same year, Sun played the title character in the television series, Auntie Duohe, based on the novel of the same name by acclaimed Writer Geling Yan.

Sun has been married to actor Deng Chao since 2010. They have two children, a son named Deng Han Zhi and a daughter named Deng Han Yi.

For her role as an independent mother in Hot Mom! (2013), Sun won the Best Actress award at the 20th Shanghai Television Festival. She also won the Most Popular Actress award at the 10th China Golden Eagle TV Arts Festival.

In 2015, Sun played Queen Dowager Xuan, the first stateswoman in China, in historical drama The Legend of Mi Yue. The series was a commercial success, and recorded the highest ratings of the year. Sun won her second Best Actress trophy at the 22nd Shanghai Television Festival. The same year, Sun challenged her first comedy role in Devil and Angel, directed by her husband Deng Chao.

In 2017, Sun played the titular character in the period drama Nothing Gold Can Stay, based off a real-life story of Zhou Ying, a budding businesswoman who takes on the responsibilities from her dead husband and starts rebuilding their Business empire from scratch. For her performance in the role, Sun was awarded the Outstanding Actress award at the Flying Apsaras Awards.

In 2018, Sun was cast in Zhang Yimou's upcoming film, Shadow as the female lead.

Sun expressed her stand against animal cruelty by featuring in PETA Asia’s anti-fur ad in 2010.