Deng began playing table tennis at age five, and four years later she won her provincial junior championship. She was age 13 when she won her first national championship. Despite her success, she was initially denied a spot on the national team because she was so short (she stood only 1.5 metres 【4 feet 11 inches】 tall). Her talent, however, could not be denied, and she was finally included on the national team in 1988. She teamed with Qiao Hong to win her first world championship title in the women's doubles competition in 1989. Two years later Deng won her first singles world championship. At the 1992 Olympics in Barcelona, Spain, she won a gold medal in both the singles and doubles competitions and repeated the feat at the 1996 Olympics in Atlanta, Georgia. She also earned singles and doubles titles at the 1995 and 1997 world championships.

After retiring at the end of the 1997 season, Deng served on the International Olympic Committee's ethics and athletes commissions. She also was a member of the Beijing Organizing Committee for the 2008 Olympics.