The team will face China, North and South Korea, Guam, Japan, Macau, Mongolia and Taiwan in 289 events in 24 different sports, including athletics, football, gymnastics, swimming and wushu.
The competition, last held in Hong Kong in 2009, ends on October 15. From 2017, it will become the East Asian Youth Games.
Young Post asks three athletes about their hopes and expectations
Andy Lau Chun-hin, 19, Tennis
The 1.78-metre-tall right hander, who is a full-time professional, finished his secondary school studies in Australia last year.
The Hongkonger has just moved back home from his training base in Guangzhou to join his coach, Alan Ma, who is in charge of Hong Kong Tennis Association's junior elite players.
Andy, ranked Hong Kong's number-one junior at the end of last year, has never represented Hong Kong at any level before. So he is looking forward to making his competitive debut.
"I'm playing in the singles, and in the doubles with Brian Yeung Pak-long," Lau says.
"My friends from Taiwan, who have trained with me in the past, will be at the Games. Some are ranked about 300 in the world, so I face a tough challenge.
"I'm just going to try to do my best, and hope I will play for Hong Kong many times in the future."
Coby Lau Pui-sze, 18, Form Six, Good Hope School, Hockey
Coby has just played in her first senior international tournament for Hong Kong. They came last out of eight teams at the eighth Women's Asia Cup, which ended in Kuala Lumpur, Malaysia, last Sunday.
She took up the sport at school only three years ago. After a year, she joined Hong Kong's junior squad, and moved up to the senior team the next year. "This year is an important one for Hong Kong's hockey players," Coby says. "We've had some important matches, including qualifiers for the National Games in May, last week's Asia Cup, and now the East Asian Games."
Coby says the team will play a round-robin tournament against Japan and China - both likely to prove too strong for them - and Taiwan in Tianjin. "We're about as good as Taiwan," she says. "We lost narrowly to them in the Asia Cup.
"We've had little time to work on improving our game since the last competition, but will do our best."
Devin Chung Wai-sze, 22, Year Two, City University, Volleyball
Devin played for Hong Kong at July's Universiade - a multisport international competition featuring more than 10,400 university students, in Kazan, Russia.
The team beat the United States, the United Arab Emirates and Macau while finishing 18th out of 20 volleyball teams.
Some of Devin's Universiade volleyball teammates will join him to compete at the Games.
"We overdid our things before the Universiade, training six days a week and also playing club matches," says Devin, who plays as setter. "I think we got tired and struggled to be at our best."
Devin says that Hong Kong's volleyball players have matured as a team and should do well at the Games.
"I think we learned a lot when competing at the Universiade," Devin says. "Now, hopefully, the coaches have prepared a strong game plan for us so we'll be able to perform to our potential."
At the 2009 Games, Hong Kong finished fourth in the rankings after winning 26 gold, 31 silver and 53 bronze medals.