These trains carried 131,000 TEU last month, up 40 per cent year on year, reports Xinhua.
As of the end of May, 40,000 trips with about 3.55 million TEU had been made via the intercontinental rail route.
The freight trains had reached more than 160 cities in 22 European countries, data from the NDRC shows.
Deputy NDRC chief Ning Jizhe stressed that China will step up efforts to coordinate the rail services with economic and trade cooperation.
More work will be done to upgrade some major customs and railway sections to improve services and infrastructure along the train route, Mr Ning said.