USD/CNY was quite volatile yesterday.  The pair broke 6.54 levels in the morning of London trading session.  It is observed that in past few days the Chinese corporates are preferred to hold US dollar on hand, that cause the dollar to be stronger against Chinese currency.

Meanwhile, in order to slower the pace of Yuan depreciation, the China's central bank should sell USD.

"In our view, when PBoC set USD-CNY fixing at above 6.40 this Tuesday, this kicked off a "stress test": the central bank needs to see the market response to a weaker CNY, and unfortunately this test needs to be done before the Fed's rate hike. So far, we have seen the results of this test: the demand for USD is substantial. That said, the central bank will continue to sell USD when market enters a "panic mode", but the trend of CNY/CNH weakness is inevitable", says Commerzbank.