From car makers to wine growers to tech firms, Europeans have for years looked to China to bolster sales as growth prospects back home have flagged.
But only 28 per cent of firms polled by the European Chamber of Commerce in China said they were "optimistic" about their profitability in the country, which the group said was an "all time low".
The number of respondents who see China as a "top three" investment destination fell to 58 per cent this year, the lowest since 2011, it added.
"European companies fortunately know how to deal with difficulties," Joerg Wuttke, Chamber president, told AFP. "But the longer the companies are here in China, the less optimistic they are."
China's economy grew 7.4 per cent last year, its slowest pace in 24 years and the slowdown has continued into this year.
The Communist Party has vowed to shift the economy away from big-ticket investment projects and towards personal consumption, while also fighting graft and clamping down on anti-monopoly behaviour.
China has in the past year launched anti-monopoly probes against a number of high-profile foreign firms, drawing accusations of double-standards as domestic players are allowed to dominate some markets.
A third of respondents believe that China's ambitious reform agenda has not "helped create an even playing field for foreign investors," the report says.
It added: "The pace of the implementation of the reform agenda still lags behind the expectations of European companies."
Respondents also cited slow Internet speeds and online censorship as barriers to business.
He added that while some companies were looking to other emerging markets as a source of growth, so far they were staying put.
"The optimism is shrinking but the optimism is still there," he said. "We don't see European companies leaving China."
For many years, he added, it was just China that drove their growth, but "now basically, they have options and other choices".
