Authorities in the commercial capital Shanghai warned bullet train services might be affected by the storm -- a sensitive issue after a deadly high-speed train crash two weeks ago that was initially blamed on weather conditions.
Muifa, which was packing winds of up to 162 kilometres per hour (100 miles per hour), is expected to make landfall on China's east coast at the weekend.
The National Meteorological Centre said the typhoon was forecast to land in Zhejiang or Jiangsu province, both of which neighbour Shanghai, on Saturday evening or during the day on Sunday.
The official Xinhua news agency said 7,000 fishing boats had been called back to harbour and local governments were preparing for possible evacuation of residents.
Strong winds, torrential rain and waves of up to 2.5 metres high were expected in coastal areas.
The typhoon could also affect the eastern provinces of Anhui, Jiangxi and Shandong, the Ministry of Civil Affairs warned.
The storm decreased in power on Wednesday night, going from a super typhoon to a severe typhoon, but is still expected to be one of the most powerful storms to hit China in recent years.