China has been a member of the World Trade Organisation (WTO) since 2001 but it is not recognised as a market economy by any of its major trading partners, including the EU and the US. China's WTO Accession Protocol allowed WTO members not to grant “Market Economy Status” (MES) to China for a period up to 11 December 2016.
Not applying MES to China allows the EU to use alternative methods for calculating dumping margins (that apply to Non-Market Economies, NMEs, often based on the higher prices applying in third countries).