"For those iron ore imports that are moved from the port before June 1, the storage fees will follow the earlier standards," the notice said.
Analysts said that the move is likely to help clear the record stockpiles at ports, as it significantly raises the costs to trading firms, and it will help to bring down spot iron ore prices as well - as the government hopes.
China's National Development and Reform Commission, the country's top economic planner, held a joint meeting last week with government departments, steel mills, and trading firms to discuss how to clear the record high stockpiles.
Earlier this week, the China Iron & Steel Association also asked its member companies in a statement to clear stocks at the ports and control further imports.
The measures are believed to be part of the Chinese government's latest efforts to increase the bargaining power of Chinese steel mills in talks with miners BHP Billiton and Rio Tinto on iron ore prices.