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.
Indonesia rescue agency recovers another victim from capsized ship
Police arrest Pakistan ex-PM Imran Khan's sister in Lahore
Two dead in Moscow region, drones hit oil refinery in Russian capital
US says it killed four people in strike on vessel in Caribbean
Saudi civil defence sends all-clear after alerts issued for capital Riyadh
