Chengdu 2021 say the number of registered city volunteers for the International University Sports Federation (FISU) Summer World University Games has exceeded 690,000.
Chengdu 2021 created an online platform where young people can register to volunteer.
The organisation revealed in October that the number had surpassed 500,000, but now claims this has risen further to over 690,000.
Organisers say that more than 20,000 volunteers will be required for the Games.
A total of 5,000 have already been selected from the volunteer pool.
The volunteers took part in online tests before being confirmed for their respective roles.
Chengdu 2021 say more than 200 online and offline training sessions have been held for volunteers to date.
Organisers are expected to unveil a volunteer logo, as well as a nickname and slogan, in the coming weeks.
Chengdu 2021 is set to run from August 17 to 29, having been pushed back slightly following the postponement of the Tokyo 2020 Olympics.
It is due to be the third time that China will host the Summer World University Games, following on from Beijing in 2001 and Shenzhen in 2011.
There are 18 sports on the programme.