"The joint venture agreement has a strong monopolistic color and Chinese steel mills will resolutely oppose the agreement," the CISA said in a statement on its website.
"The iron ore trade is gradually advancing in the direction of monopoly," the association said. The joint venture has a direct bearing on the interests of Chinese steel plants as China is the biggest buyer of Australian iron ore, it added.
China should have a say in the iron ore trade, especially in Asia, according to the statement.
The CISA said it will allow no market speculation on iron ore trade on the domestic market. It also urged regulators to revoke the licenses of these iron ore importers which were found to have engaged in speculation.
Rio Tinto scrapped a proposed $19.5 billion of investment by Aluminum Corp of China, or Chinalco, on Friday.
The world's third-largest mining company has announced a joint venture with BHP Billiton, the world's second-largest. In the agreement, BHP would pay Rio Tinto $5.8 billion to jointly run iron ore resources of both companies in west Australia.
Mei Xinyu, an economist with the Ministry of Commerce, told Xinhua Monday that China should closely watch the joint venture process and be ready to work with other countries to curb market manipulation when necessary, with the help of anti-monopoly law.