China's national Social Security Fund (SSF) will be more than doubled to 300 billion US dollars in 2015, the SSF chief Dai Xianglong said Sunday.

The fund's current size is 130 billion U.S. dollars, Dai said at the annual conference of Boao Forum for Asia in south China's island province of Hainan.

The SSF is ready to buy into unlisted companies and invest more in private equity funds this year, said Dai, chairman of the National Council for Social Security Fund.

The agency has invested 6 billion to 7 billion yuan (1.02 billion U.S. dollars) in five local PE funds, he said. The cap of investment in PE funds is 10 percent of its total capital.

Dai, also the former central bank governor, said China needs not only to attract foreign investment but also to expand channels for Chinese investment overseas as the country's foreign exchange reserves has risen to 2.4 trillion U.S. dollars.

But the central bank should not buy a huge amount of foreign currency and inject equivalent yuan into the financial system, as it could lead to capital bubbles, he stated.

"The move is no good for us. We need to increase overseas investment," he said.

The SSF will also work to promote cooperation between the emerging economies, he said.

The emerging economies will contribute more to global economic growth in the next 10 to 20 years, but they also face growth challenges, including inflation, transformation of economic growth pattern and volatile international capital flows, Dai said.

The emerging economies face pressure on inflation after explosive growth in lending last year aimed at reviving growth amid the financial crisis, Dai said.

The export-driven growth in countries like China not only costs a huge amount of resources, but also leads to many trade frictions, he said, adding that the future growth should stress more on consumption.

He also expressed the worry over international capital volatility faced by the emerging economies. He said inflows of hot money had inflated asset bubbles in China.