Chief financial officer Friedrich Eichiner said the world's most populous country, a robust source of growth for German car manufacturers in recent years, was now a riskier market.
"The second half will be more heavily burdened by investments, development costs and personnel costs," Eichiner told a telephone conference.
"If the challenges in the Chinese market increase, we cannot rule out an impact on our forecasts."
BMW said it had sold 230,700 cars in China during the first half, a modest increase of just 2.3 per cent compared with the same period last year.
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China remains the world's biggest car market but a slowing economy, rollercoaster stocks and car plate restrictions in some cities to reduce pollution have hurt demand.
China's overall auto sales reached 23.49 million vehicles last year, jumping 6.9 per cent from 2013, but its Association of Automobile Manufacturers expects the increase to slow to around three per cent this year.
Munich-based BMW had earlier reported that its second-quarter profits fell by one per cent, a figure that nevertheless was better than analysts predicted.
Analysts polled by Bloomberg had predicted net profits of 1.66 billion euros.
Sales of its main BMW brand cars grew by 4.9 per cent on last year, while the company said it sold almost a quarter more of its Mini cars.
However, sales of its luxury Rolls-Royce cars were disappointing, falling back 7.7 per cent in the second quarter.
Overall turnover grew by a fifth to nearly 24 billion euros, exceeding market expectations.