China says the US has overtaken the European Union as its biggest export market, as the continent's debt crisis has sent demand slumping.

"The biggest is the US and the EU is second," Commerce Ministry spokesman Shen Danyang told reporters at a regular briefing.

"The EU used to be the biggest."

China's exports to the United States in the first 10 months of this year totalled $US289.3 billion ($A279.18 billion), while shipments to the EU came to $US276.8 billion ($A267.12 billion), according to Chinese customs figures.

Weak demand from both Europe and the US has been a big factor as China's economic growth has slowed over the past seven quarters to the end of September.

Economic growth in the United States remains weak but is expanding, while the eurozone's debilitating debt crisis has dragged it back into recession.

Shen also said the Association of Southeast Asian Nations had moved past Japan as China's third-biggest export market.