Krosa made landfall along the boundary of densely populated Zhejiang and Fujian provinces a day after killing four people in Taiwan, the Xinhua News Agency said, citing local weather officials.
As of 8:30 a.m. on Sunday, Taiwan's Central Weather Bureau said Krosa had weakened to a tropical storm with sustained winds of 66 mph, down from 114 mph.
More than 1 million people were evacuated from low-lying coastal areas, including more than 500,000 tourists who were at beach resorts for the National Day holiday week, the Chinese government's Xinhua News Agency reported.
On Saturday, Krosa killed four people in Taiwan as it knocked out power to 2 million homes and drenched the island with torrential rains, according to Taiwan's Disaster Relief Center.
Two men were killed in suburban Taipei when a landslide buried their house, the center said. A man died after falling from his balcony in Hsinchu and a woman was electrocuted after falling from her motorcycle in Tainan. The agency said two other men were missing.
Early Sunday, China's coast guard rescued 27 sailors from a Hong Kong freighter that suffered mechanical failure after it was hit by Krosa off the southeastern port of Wenzhou in Zhejiang, the Chinese government's Xinhua News Agency reported.
Schools were closed and airline flights canceled in Wenzhou, which lay in the storm's path, Xinhua said. The city ordered fishing boats, ferries and sightseeing boats to return to port.
In Fujian, which was hit by torrential rains ahead of Krosa's arrival, authorities warned of possible mudslides, Xinhua said.
In Shanghai, where the Special Olympics is taking place, the city government canceled vacations for flood-control workers and was drafting plans to drain competition sites, the agency said.