With winds up to 151km/h (93mph), the storm landed in Fujian province early on Monday, bringing heavy rains and causing widespread power cuts.
The authorities earlier issued the highest alert – red – for the area.
At least two people have been killed by the typhoon, state-run news agency Xinhua reported.
One victim was on his way to rescue a fisherman when he was blown off a hill by strong winds late on Sunday, Xinhua said.
Some homes are said to have collapsed in neighbouring Zhejiang province and two port workers are missing.
Typhoon Fitow – named after a flower – made landfall at 01:15 local time on Monday (17:15 GMT Sunday) in the city of Fuding, Chinese meteorologists said.
The typhoon had affected over three million people in Zhejiang and caused economic damage of over 2bn yuan ($330m; £200m), Xinhua said, citing the provincial flood control office.
Parts of China have been hit by up to 200mm (8 inches) of rain, AFP news agency reported.
Over the weekend the authorities drafted in the army to help strengthen flood defences, the BBC’s John Sudworth in Shanghai reports.
Hundreds of thousands were evacuated before the storm hit the coast.
Ports are at a standstill as boats have been ordered to take shelter.
The strong winds did not deter some people from venturing outside.
In Fujian, 177,000 people were evacuated before the storm hit the coast, Xinhua said, while in Zhejiang, some 574,000 people had to leave their homes.
Some 35,000 boats in Zhejiang and 30,000 in Fujian were ordered to return to harbour for shelter.
Coastal facilities such as seaside bathing centres were also closed, state media reported.
Dozens of flights to and from Wenzhou airport in Zhejiang were cancelled.
The storm is now moving north-west and is expected to weaken quickly.
Typhoon Fitow is the 23rd tropical storm to hit China this year, Xinhua reported.
It comes just weeks after Typhoon Usagi killed at least 25 people in southern Guangdong province.