This year, China has six cities ranked among the world's 55 first-tier cities, according to the Globalization and World Cities Study Group and Network, or GaWC.

The leading global rating agency grades cities on four levels, including Alpha, Beta, Gamma and Sufficiency. Each level has two or four ratings indicated as +/-, based on indicators that business and professional services, including banking, insurance, accounting, law, advertising and management consulting, say are essential to support economic development.

In addition, the city's GDP and output value from manufacturing are not contained in the rating indicators.

China's Hong Kong, Beijing and Shanghai ranked among the top 10 world cities, and were at the Alpha+ level.

Let's take a look at the top 10 world cities.

No 10 Tokyo, posted at Alpha+ level