The former Tottenham player, 29, is the Spanish club's first signing since Neymar left to join Paris St-Germain in a world record transfer.
Meanwhile, Barca's Uruguayan forward Luis Suarez will be out for "four to five weeks" after he was injured in the Super Cup defeat by Real Madrid.
He will also miss World Cup qualifiers against Argentina and Paraguay.
Paulinho joined Tottenham for £17m from Corinthians in 2013, before moving to China in 2015.
He helped Evergrande win last season's Chinese Super League and leaves the team top of the table in the current campaign.
Paulinho said: "You have to face challenges with courage. I will try to do my job and I am prepared. It's a very satisfying moment. The dream I have been looking for has come true. I will give everything."
Barcelona are also keen on Liverpool midfielder Philippe Coutinho and Borussia Dortmund forward Ousmane Dembele.

The incident happened at Unst harbour about 06:50. There were no passengers on board, only four crew members and no-one was injured.
There was no loss of fuel from the vessel.
The ferry is currently alongside in Unst with the fire brigade pumping out water which was taken on board during the accident.
Barcelona have signed Brazil midfielder Paulinho from Chinese club Guangzhou Evergrande for 40m euro (£36.4m).
[NEXT_CONCEPT]
Shetland Coastguard was called out after the inter-island ferry hit rocks on its way from Yell to Unst.