Su Rong, 65, until last year the top Communist party official in the central province of Jiangxi, was "removed" from his most recent post as vice-chairman of the China People's Political Consultative Conference (CPPCC), the official Xinhua news agency reported.
Such a removal is usually a prelude to criminal prosecution.
He is the most senior politician to be investigated since Xi Jinping ascended to the top of the party in 2012.
A number of government officials - mostly at the local level - as well as bosses at state-run firms, have faced corruption probes since Xi took over and called graft a threat to the organisation's future.
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But critics say weak rule of law and a lack of governmental transparency have reduced the impact of his campaign.
The CPPCC is a discussion body that is part of the Communist party-controlled governmental structure.
Su was also previously the top official in the northwestern provinces of Qinghai and Gansu, giving him rich connections in China's fictionalised political system.