I'll visit nanchang 2 weeks later like transfer.One day stay in the city and next day have a flight.

Well, I'd suggest you stay near Bayi Square and the nearby Bayi Square North bus stop has shuttle bus line 1 to the airport. The recommended hotels are 7 Days Inn on South Guangchang Road and GreenTree Inn on Zhongshan Road. Try to search them online and book.

For sightseeing, the Bayi Square itself is for free and near the square the Aug. 1st Uprising Memorial Museum is suggested. Then walk for 10-15min to the Bayi Park for roaming around. The three sites are enough for a day.