US companies in China are shifting their focus to the service sector in line with China's transition from being the world's factory floor to a knowledge-driven economy, a survey has found.

For the first time, services accounted for more than half, or 52 percent, of US companies' revenue in China in 2013, up 11 percentage points from the previous year.

This is according to the annual China Business Report released on Tuesday by the American Chamber of Commerce in Shanghai.