How to go to Mt. Lushan National Park in Jiujiang from Shanghai? And what is the price and transport time?

You can fly to Jiujiang airport. Then take the airport shuttle bus to JJ Bus Station, where you can find frequent buses for Mt. Lushan.
The flight tickets price is hard to tell because you can get a large discount if you book in advance. The Eastern Airline has the flights to JJ, so you can find more information on the official website of Eastern Airlines. The flight takes about one hour and a half.
The bus from the JJ Bus Station to Lushan costing about 15RMB per person.