Weeks after he was removed as railways minister, a published media report said Liu Zhijun pocketed more than 800 million yuan (US$122 million) in kickbacks from companies that did business with his powerful office.
The report said that the former minister also enjoyed the company of at least 10 mistresses including actresses.
Liu was directly in charge of building China's high-speed railways, the Hainan-based New Century Weekly reported Monday.
Liu was removed from the post for "severe discipline violation."
He allegedly received 822 million yuan (US$125 million) from companies eager to win contracts for China's booming high-speed railway projects including many State-owned enterprises.
Liu became railways minister in 2003 and he mapped China's high-speed railway strategy, which covers numerous new projects.
The annual investment in high-speed railways multiplied year after year and surpassed 700 billion yuan (US$106 billion) last year.
As minister, his most profitable under-the-table deal was with the Shanxi-based railway supplier Ding Shumiao, who had a close personal relationship with Liu.
Ding was put under investigation in early January, according to sources familiar with the matter.
Liu received kickbacks mainly for eight railway construction projects, and allegedly received about 2.5 to 4 percent from each contract signed.
Ding allegedly obtained 422 million yuan (US$64 million) to introduce bidding companies to Liu, according to the report.
The Beijing-based Economic Observer newspaper reported Sunday that Liu allegedly assigned Ding's Broad Union Investment Management Group to be the sole supplier for many types of construction materials for high-speed railways, including protective barriers, and charged two to three times more than the market price.
However, authorities have not confirmed such allegations.