If i arrived at Wuhan Airport 11.30 pm midnight, what is the transportation to city centre?

Don't worry. You can still take the airport shuttle bus Hankou Line to get to downtown area. The service hours of this bus route will until the last flight arrival. And you will arrive at Southeast Hospital. It takes around 70 mins. And the ticket fare is 17 per person. After arriving, you can take the taxi to the destination.
Besides, you can find the official cabs waiting outside of Gate no.6-7 of the Terminal Building. If by taking it from the airport, it will spend CNY 70-80 at night.
You can choose the way you like.

Thank you lily.is the city taxi 24 hours???

Yes, generally speaking, there are still several cabs on the street in the midnight/early morning. Don't worry.