Zheng Yanxiong is known for dealing with a land dispute in southern China in 2011.
His new agency's remit will be to enforce a strict security law passed this week in Hong Kong.
Critics of the law say it erodes the territory's freedoms.
Crimes of secession, subversion and terrorism will be handed punishments of up to life in prison.
Separately, one of 10 people arrested under the new law during protests on Wednesday has become the first to be charged under it.
Hundreds were detained during the clashes.


Russian strikes kill 16 in Ukraine's Kyiv
Prince Harry and Meghan to move back to Britain
North Korea launches 10 ballistic missiles as US-South Korea drills near end
Kenya tourist helicopter crash kills seven
US, South Korea to cut length, scope of military drills after Trump order
