How many times I can get Visa On Arrival in China with Australian passport ?

You can get VOA as often as you want because there is no limit on how often and how many times you will apply for this specific visa. Anyway, you are warned that you cannot rely on Shenzhen VOA if you want to arrive in Shenzhen by air. This is definitely not a way how you can get a VOA because the airport staff in your origin country will not allow you to board the plane! You are advised to apply for a VOA after you have arrived in Hong Kong or Macau. Of course, you are perfectly allowed to leave Shenzhen using Shenzhen airport for your direct flight to some other country.

By the way, if you want to use Shenzhen as your arrival airport and also Guangzhou to reach Hong Kong and Macau, you can do that by relying on visa free transit option. If you use Shenzhen airport, you can only rely on 144 hour visa free transit and if you use Guangzhou, you can rely on 24 and 144 hour visa free transit to reach Hong Kong and Macau.

If you use 144 hour visa free transit through Shenzhen to reach Hong Kong your itinerary will be:

X country - Shenzhen - Hong Kong

Please keep in mind that you will have to book your ferry ticket from Shenzhen Shekou ferry port to Hong Kong online in advance through CKS - Chu Kong Passenger Transport company website, but you should have in mind that your departure from Shenzhen by ferry has to be at least 24 hours and 1 minute after your scheduled arrival by plane. In other words, you have to stay in Shenzhen for a little bit more than 24 hours to be eligible for 144 hour visa free transit.

If you use Guangzhou airport, you do not have to wait for 24 hours to elapse, but you can immediately depart from the airport toward Hong Kong.

Of course, this is possible if your citizenship belongs among the group of countries that are eligible for 144 hour visa free transit scheme.

Thanks for your reply Zupan,
But I’m going to Xiamen and I want to get VOA from there and after 5 days fly out to Hong Kong and fly back to Haungzhu and get another 5 days VOA.
I just wanna know if that is possible or not ?

No, it is not possible to obtain a Xiamen VOA any more. You should consider it as a relic of the past. You have to create visa free transit eligible itineraries based on the model:

Country A - Country B (Xiamen, China) - Country C

You can definitely use eligible territories (Hong Kong, Taiwan and Macau) in the same way as if they were countries. You should just creatively use the flights between Hong Kong, Macau, Taipei and Xiamen and you will be perfectly allowed to enjoy your travel to Xiamen absolutely visa free, enjoying 144 hour visa free transit. Anyway, you should definitely forget about Xiamen VOA!