The two countries are both exporting giants -- with Germany the EU's biggest economy and China the world's second-largest -- and Merkel was looking to strengthen their economic relationship on her three-day visit, her seventh since coming into power in 2005.
She was accompanied by executives from Siemens, Airbus, Lufthansa and Deutsche Bank among other companies, according to German media.
Merkel and Premier Li Keqiang oversaw the signing of a series of agreements today.
The new plants' production capacity will be finalised "based on market demand and relevant industrial policies", the company said in an email to AFP.
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Merkel toured a Volkswagen factory in the southwestern city of Chengdu yesterday.
China has become Volkswagen's largest and most important market, the company said, adding the group sold more than 1.5 million vehicles in the country in the first five months of this year, including sales by its joint ventures FAW Volkswagen and Shanghai-Volkswagen -- up 17.7 percent year-on-year.
The helicopters -- mainly light single-engine aircraft from the Ecureuil family and the light twin-engine EC135 -- will be used for general aviation activities, it said in a statement.
No financial details were provided.
"It is evident that China's relaxation of its low-altitude airspace regulations is enabling the country's burgeoning helicopter market to realise its potential," Airbus Helicopters CEO Guillaume Faury said in the statement.
Also today German airline group Lufthansa said it had signed a memorandum of understanding to form a joint venture with Air China.