Yes. There is no age limit.
If your child is taller than 1.4-meter, he must apply for a badge. Otherwise, just enter with you.
There is no minimum age for children from Overseas to enter the Fair but there is a requirement as followed:
Children below 1.4 meters high can enter the Fair free of charge with their parents by showing their valid passport, Hong Kong or Macao Home-return Permit, or Taiwan Compatriot Travel Certificate.
Children over 1.4 meters high (including 1.4 meters high) should present a valid passport, Hong Kong or Macao Home-return Permit, or Taiwan Compatriot Travel Certificate to apply for the Entry Badge at the Fair with their parents. It will cost 100RMB as service fees. Besides, one identification photo in blue or white background (4cm x 5cm) is required. As there will be lots of people at the Fair, parents should take good care of their children in case they get lost.