You asked if a national of China needs a visa to pass through the UK in transit.
Yes, you need a Direct Airside Transit (DAT) visa, unless you qualify for exemption because you hold:
a valid US/Canadian visa and also hold a ticket to or from the US/Canada routed via the UK. This will include a period of 48 hours after the expiry of the US/Canadian visa for those leaving the US or Canada to allow for those who choose to leave at the very end of the validity of their visa;
a USA I - 551 Permanent Residence Card (Green Card) issued on or after 21 April 1998;
a US Immigrant Visa and Alien Registration - Form 155
an expired I - 551 Permanent Residence Card and a valid letter authorising its extension from a US Embassy/Consulate;
a Canadian Permanent Residence Card issued on or after 28 June 2002;
a valid Category D visa issued by EU/EEA member states;
a common format EU residence permit issued under Council Regulation (EC) No 1030/2002.