Hello , am Belgium citizen ask for 144hours or 72 visa

If you fly non-stop Hong Kong-Guangzhou-Dubai you can stay 72 hours without a visa. You will need a visa if you want to stay longer (there's no 144 hours visa-free in Guangzhou). By the way, you would need a visa if your flights were Hong Kong-Guangzhou-Hong Kong-Dubai, or if you travel by land from Hong Kong to Guangzhou.

Thank you.

I will fly from Dubai to HK and stay in HK one day then next day fly to Guangzhou.
I stay in Guangzhou 72h to visit canton fair then fly back to Dubai.

Do I need to apply for 72h visa when arrive to Guangzhou airport?
I am Belgium citizen.

Thank you.
Yousif

You need to print your confirmed Guangzhou-Dubai ticket and show it at check-in/boarding in Hong Kong, and tell them you will be in "transit without visa" (it's not a visa). You will also need to show your ticket on arrival in Guangzhou. It can also be helpful to print your hotel confirmation in case Guangzhou immigration want to see it.