Mines Minister Mahmoud Thiam said Tuesday that the Chinese firm "will be a strategic partner in all mining projects" in the West African country. He did not name the company involved.
Guinea has the world's largest reserves in bauxite and appreciable quantities of gold and diamond deposits.
The arrival of the Chinese puts them in direct competition with the American-owned Guinea Bauxite Company CBG and the Russians' RUSAL.
The Russians have been in a legal tussle with the junta over whether the mines are owned by Guinea's government.
Africa's trade with China reached more than $100 billion in 2008, according to the African Economic Outlook.