A well known industry figure in China and overseas, Wen joined the association in 2001 after graduating and working as an engineer, becoming a vice chairman in 2008.
China churned out a mere 3.6 million tonnes of primary aluminium in 2001, according to official data. It is now by far the world's top producer and consumer of the metal, with last year's output hitting a record 37 million tonnes.
"Despite such a serious pandemic in 2020 and 12 trade remedy investigations, smelters and fabricators ... have increased their production, consumption and efficiency regardless," Wen, who is in his late 50s, told Reuters.
He represented Chinese aluminium companies in negotiations with the United States as Washington slapped anti-dumping duties on Chinese aluminium products in 2017. It continues to accuse China of creating excess capacity.
Admitting the last few years had been hard work, Wen said he is looking forward to some rest in his retirement but will be on hand to provide advice to companies and local governments.
He was last month named an independent director at private-sector aluminium giant China Hongqiao Group and holds the same position at Henan Shenhuo Coal & Power and China Zhongwang Holdings.
It is unclear who will replace Wen at the association, which on Wednesday said in a statement to Reuters it would decide on a new aluminium leadership team as soon as possible.
(Reporting by Tom Daly; Editing by Rashmi Aich and Jacqueline Wong)