The storm made landfall in Zhoushan, a city east of the port of Ningbo in Zhejiang province, dumping more than 100 millimeters (4 inches) of rain since late Friday, China Central Television and the Xinhua News Agency reported.
Xinhua said no deaths or injuries had been reported by Saturday evening.
Some 1.1 million people were evacuated from coastal areas of Zhejiang and more than 46,000 in neighboring Jiangsu province ahead of the storm, Xinhua said. The provincial flood control bureau said 28,764 ships had been ordered back to port.
The national weather service said earlier the typhoon might be the strongest to strike China since the communist government took power in 1949. It initially was deemed a super-typhoon but was downgraded at midday Saturday to a strong typhoon.
Heavy downpour was reported in some areas, including the village of Lai'ao, with more than 400 millimeters (16 inches) of rain, according to Xinhua.
The country's railway service said more than 100 trains between the region's cities were canceled through Sunday.
A total of more than 600 airline flights were canceled in the cities of Hangzhou, Ningbo, Wenzhou and Taizhou, according to Xinhua. Buses and passenger ferries suspended service.
Earlier, Chan-hom caused 20 injuries as it moved over islands in southern Japan, Kyodo news agency reported, citing the Okinawa prefecture government.
The storm dumped rain on the northern Philippines and Taiwan, where several flights were suspended. The stock market and public offices were closed Friday in Taipei, Taiwan's capital.
Chan-hom is the second major storm to hit China this week, after Typhoon Linfa forced 56,000 people from their homes in the southern province of Guangdong province.