After originally entering the 2006 NBA Draft but subsequently withdrawing, Sun decided to enter the 2007 NBA Draft and was taken by the Los Angeles Lakers as the 40th overall pick. With Sun being drafted alongside Yi Jianlian that year, it marked the first time in NBA draft history that two China-born players were drafted in the same year. That feat would not be repeated until 2016. It would also be the first time in modern NBA history that a Chinese basketball player would be drafted outside of the CBA. However, Sun stayed with the Beijing Olympians for another year before signing with Los Angeles in August 2008.