Born in Changsha, he first represented China internationally at the 2006 World Junior Championships in Athletics held in Beijing, where he finished eighth in his qualifying group. He made progress into the senior ranks in 2008, when finished as runner-up at the Chinese Athletics Championships with a personal best of 16.54 m. In the 2009 indoor season, he improved this to 16.89 m on the Chinese Athletics Grand Prix circuit. He represented his province at the 2009 National Games of China and came sixth. His first major success in the senior ranks came at the 2010 Asian Indoor Athletics Championships, where his jump of 16.73 m was a championship record and brought him the gold medal. He set an outdoor personal best of 16.86 m that year and placed third at the national championships. He broke the Chinese indoor record in February 2011, clearing 17.01 m and matched his outdoor best in April. Dong and Li Yanxi were the Chinese entrants at that year's 2011 Asian Athletics Championships, but while Li took the silver Dong only managed fifth place with 16.36 m. Just over a week later he jumped 17.05 m, albeit wind-aided. He defended his title at the 2012 Asian Indoor Athletics Championships with a championship and national record of 17.01 m, although he narrowly saw off Chinese rival Cao Shuo, who jumped the same distance but had a shorter second-best jump. In his first appearance on the global senior stage he finished eighth at the 2012 IAAF World Indoor Championships. Outdoors, a big improvement to 17.38 m in April earned him a place at the London Olympics and he reached tenth in the Olympic triple jump final – the best performance by an Asian athlete. In Nanjing in March 2013 he broke Oleg Sakirkin's 20-year-old Asian indoor record with a jump of 17.16 m. That year, he also reached the final of the World Championship. His performance at the 2015 World Championships was less good, failing to make the final at a home World Championships. He began 2016 well, setting a new area and national record indoor in February at the Chinese National Indoor Grand Prix, before going on winning the World Indoor Championship in March. He then set a new outdoor personal best on the way to winning the bronze medal at the 2016 Summer Olympics.
