The ruling Chinese Communist Party has "decided to suspend Miao Hua from duty pending investigation", Wu Qian, a spokesman for Beijing's defence ministry, told a press briefing.
Wu did not provide further details about the charges against Miao, an admiral and a member of Beijing's powerful Central Military Commission (CMC).
But "serious violations of discipline" are commonly used by officials in China as a euphemism for corruption.
Miao sat on China's Central Military Commission alongside five other men, including President Xi Jinping at the top.
He headed the CMC's Political Work Department, the top military body's most important office.
Miao has been described as a "close ally" of Xi and a "trusted interlocutor" between the military and the party by Lyle Morris, a senior fellow at the Asia Society.
Beijing has deepened a crackdown on alleged graft in the armed forces over the past year, with Xi this month ordering the military to stamp out corruption and strengthen its "war-preparedness".
The intensity of the anti-graft drive in the military has been partially driven by fears that it may affect China's ability to wage a future war, Bloomberg reported citing US officials this year.
The removal of Miao reveals the "endurance of corruption and discipline issues across the system in the PLA, despite the strong efforts made by Xi," one expert told AFP.
"I think the fact that these probes are still done, and done fairly openly and publicly, despite the obvious reputational hits, shows the resolve of Xi to really address and try to root it out," said Dylan Loh, an assistant professor at Singapore's Nanyang Technological University.
Deepening crackdown
At the same briefing, Wu denied reports that Defence Minister Dong Jun has been placed under investigation for corruption.
"The reports in question are pure fabrications," Wu said.
"The rumour-mongers are ill-intentioned. China expresses its strong dissatisfaction with such slanderous behaviour," he added.
A former navy commander, Dong was appointed defence minister in December following the surprise removal of predecessor Li Shangfu just seven months into the job.
Li was later expelled from the Communist Party for offences including suspected bribery, state media said. He has not been seen in public since.
His predecessor, Wei Fenghe, was also kicked out of the party and passed on to prosecutors over alleged corruption.
The country's secretive Rocket Force -- which oversees China's vast arsenal of strategic missiles, both conventional and nuclear -- has come under particularly intense scrutiny.
In July, a top Chinese official in the Rocket Force, Sun Jinming, was kicked out of the party and placed under investigation for corruption.
At least two other high-ranking officers connected to the Rocket Force, a relatively new unit of the Chinese military, have also been removed for graft.
"We will see many more investigations into the PLA and this will not end with Miao Hua or Li Shangfu," Alfred Wu, an associate professor at the Lee Kuan Yew School of Public Policy in Singapore, told AFP.
