The train left Yiwu West Railway Station in Zhejiang province Sunday and is headed for the British capital, according to Xinhua, China's state-run news agency.
The train is hauling household goods, bags, suitcases and garments, among other items, and will pass through Kazakhstan, Russia, Belarus, Poland, Germany, Belgium and France before it gets to London.
The trip will take two and a half weeks and cover almost 8,000 miles.
London will become the 15th European city to join what the Chinese government calls the New Silk Route.
It has the advantage of being cheaper than air freight and faster than sea.
The train is part of Chinese President Xi Jinping's vision for "One Belt, One Road" - dubbed by some as the new silk road.