As of 2014, China has the largest economy in the world. Its currency however, is not as valuable as one would expect. In 2014, 1 USD was equivalent to about 6.1 Chinese yuan. As of 2015, only 20% of Chinese trade is conducted with Chinese currency. Foreign currency is most often used in China for trade.
Use of the yuan for trade in China is actually on the rise. In 2009, the Chinese yuan was not used for even 1% of total trade in the country. There is an effort by the Chinese government to increase the value of China's currency in the hopes that it will become a global trading currency in the future.
More about Chinese economy:
China, as you know, is a dragon of the Asian continent and its currency is still weak compared with the US one. What makes a currency hard or weak? The economy is the first reason of that,isn't it?
Thanks for your comment and advice.