The trade surplus came in at $13.1 billion in December, the General Administration of Customs said. That was well short of the expected surplus of $20.8 billion after the $22.9 billion surplus recorded in November.
Exports rose 17.9% year-on-year to $154.2 billion in December, the customs office said, well wide of expectations for a 23.3% increase.
On the other hand, imports jumped 25.6% to $141.1 billion, higher than forecasts for a 24.9% rise.
The customs office said the combined export-import value of $295.2 billion for December represented an all-time high.
The sharply narrower trade surplus strengthens Beijing's argument that it is gradually reforming its exchange rate amidst criticism from the US that the Chinese currency is artificially undervalued.
In the whole of 2010, China's trade surplus totaled $183.1 billion, down from $196.1 billion in 2009.