Hong Kong and Macau enjoy special status within China as SARs (Special Administrative Regions.) They have their own immigration policies which are separate to China’s.
This means that, for the sake of your visa, going from China to Hong Kong/Macau is equivalent to leaving China and going abroad. So, if you make this journey you will lose one entry on your visa—most people are issued a double entry visa, you can check this by looking at your visa’s number of entries. If your visa is single entry, then please do not plan to visit Hong Kong and return to China after your initial entry into China, unless you plan on obtaining a new visa for China in Hong Kong. If you would like to visit Hong Kong and only have a single entry visa, then consider flying to and from Hong Kong and visiting the region at the beginning or end of your trip so that it doesn’t affect your China visa.*
In certain circumstances, you may only be issued a 30-day visa instead of the standard 60 or 90 days. When this happens, if you have a double-entry visa, then you can make a trip to Hong Kong/Macau to activate the next 30 days (this is applicable if you hold a double- or multiple-entry 30-day visa). If you only hold a single-entry 30-day visa and need longer, then you may extend within China or otherwise visit Hong Kong/Macau to apply for a visa from our recommended agent there. If you are from the UK, USA or Canada, as well as many other countries, then you do not need a visa in advance of travel to Hong Kong or Macau.
If you need more advice on this, please don’t hesitate to contact us.
*Please note, in 2016 one applicant made a mistake which you should try to avoid. They chose to fly into Hong Kong with a stop in Beijing where they planned to undertake tourism for 2 days. They then flew to Hong Kong and re-entered China from Hong Kong where they found out the visa had expired because it was only single entry and they had stamped their single entry in Beijing already and then left to fly to Hong Kong. In the end, they had to stay in Hong Kong for 3 days to get a new visa, at some expense. If you have a similar plan to this, please make sure you check that your visa has more than one entry.
If you wish to fly into China for a short period and fly out again, then you could also take a 72- or 144-hour visa on arrival in a major city such as Beijing, Shanghai, Shenzhen or Tianjin. Please read more here: https://www.travelchinaguide.com/embassy/visa/free-72hour/faq.htm Make sure you meet all of the eligibility criteria if you wish to try this. Particularly, when you fly from overseas to China make sure the airline is informed that you will request a visa on arrival, they then communicate with the Chinese immigration officials. A key stipulation is that this visa can only be obtained if you have onward tickets to a 3rd country within 72 or 144 hours of arrival into China. A 3rd country means a country other than your home country or China, Hong Kong/Macau/Taiwan count as 3rd countries in this law.
If you have queries about this, you can try calling the airport immigration teams on these numbers: https://www.travelchinaguide.com/embassy/visa/free-72hour/faq.htm