The capital account deficit expanded to USD 81.6 billion (502 billion yuan) compared with USD 16.2 billion in the April-June period.
There was surplus of USD 94 billion, the State Administration of Foreign Exchange (SAFE) said.
The capital account deficit comes as China invested more aggressively overseas using the huge current account surplus accumulated through foreign trade, state-run Xinhua news agency reported.
The third quarter's current account surplus stood at USD 81.5 billion.
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Flush with nearly USD 4 trillion of forex reserves, China is stepping the outbound investments even as it made strong efforts to continue to attract foreign direct investment.
According to official data, China received USD 87.36 billion in FDI so far this year with a slight dip compared to last year but on course for an official target of USD 120 billion.
For the first nine months, China's Outbound Direct Investment (ODI), stood at USD 74.96 billion up 21.6 per cent compared to last year.