Private-equity investors in China are facing tougher times.

The slump in share offerings has made it difficult for them to sell their holdings, often in unlisted companies, via the stock market. Selling stakes to other companies, an exit strategy commonly used in the West, hasn't provided much relief.

Private-equity firms operating in China received $2.1 billion in the first half of this year from the sale of investments, less than half the amount in the same period last year, according to the Hong Kong-based Center for Asia Private Equity Research.

The number of investment exits has fallen, too, to 104 in the first half of 2012, down from 162 in the first half of 2011, it said. Firms are holding investments for longer, at an average of 59 months in the first half compared with an average of 56 months in the first half of 2011 and 44 months in 2008.

"Private-equity investors are holding for now, hoping that the [initial public offering] market will come back later this year," said Bruno Roy, a Beijing-based consultant at McKinsey & Co.