Tianjin looked at the possibility of a move for the Spain international during the January transfer window and are now set to reignite their interest at the end of the current campaign.
Any deal is likely to be extremely lucrative, with some reports suggesting that Tianjin could make Costa the world's highest-paid player with a £650,000-a-week contract.
"I can only say that we are still working on the deal [to sign Costa]. And we have already made contacts with several players," owner Shu Yuhui told Sina Sports.
"We have high standards [in buying foreign players] and those players prefer top clubs such as Bayern Munich and Real Madrid. It's safe to say that we have the same transfer targets as those illustrious clubs."