I like to go for a 1 day trip from Chengdu to a Mountain area in Sichuan. Who have a good advice?

You are suggested to tour around Qingcheng Mountain. One day is enough. You can take bullet train from Chengdu Railway Station to Qingchengshan Railway Station directly. The travel time is about 50 mins. It costs CNY 15 per person. The earliest schedule is at 06:48. After arriving, there are direct coaches that can take you to the scenic area. About the return way, the last train is at 22:18.
Have a good trip!