She was born in Los Angeles, California but moved very new to Kuwait and soon after to South Korea because of the Gulf War. She has two older sisters (Lee Eun-kyu, Lee Jin-kyu) (What is also the proud, the Korean myth that the 3rd daughter is very beautiful).

In 1998, Sunny joined the Starlight Entertainment and was in training for five years before moving to the Starworld, where he became a member of a duet called "Sugar," which never opened.

In 2007, she was nominated by singer Ayumi, moving to SM Entertainment. After nine months of training in the SM, Sunny debuted as a member of Girls' Generation that same year.

The languages ​​that are spoken Sunny Korean (Fluent), English (basic), Japanese (basic), Chinese (basic). His specialties are sports and eloquence.

His nicknames are: Soonkyu, DJ Sun, Sun, Sunny Bunny, Choi Danshin (lowest). His blood type is B and its sign is Taurus. She is 1.58 m and weighs 43kg. His position in the group is vocalist guide - along with Jessica, Tiffany and Seohyun. He studied at the Girl's High School Baehwa (배화 여자 고등학교). His "singing teacher" while still in training was the singer Wheesung.