Hi I am travelling from Chengdu to wulong karst , so what is the best plan.

Yes, you need to stay in Chongqing.
First, take a bullet train to CQ North Railway Station; and then take metro line 3 to Sigongli Bus Station.
After arrival, take a bus to Wulong Bus Station to transfer to a bus or taxi to the Karst Scenic Area.
For your 3 days’ visit, you can also enjoy other attractions in CQ, like Jiefangbei CBD, Hongya Cave, Ciqikou Village and Dazu Rock Carvings.