Hi there, I learned that there is a train departure from terminal 2 of Chengdu Airport to Emei Shan?

The ticket fare of first class seat is CNY68 and second class seat is CNY56.
The public tourist bus will stopping running to Leidongping that late. But you can hire a private car, the fare is CNY150-200 for a single trip in day time. It may be higher at night. Or maybe you will meet someone selling you hotel room in Leidongping. If you book from him/her, you can get there by their car freely.

may i ask you one more question :) may I known what time the cable start? and how much will it cost

There are two cable lines there: Wannian Cable Line and Golden Summit Line.
The Wannian line opens at 06:40 while the Golden Summit Line openes at 05:30 in high season (Jan.15 to Dec.14) and 07:30 in low season (from Dec.15 to Jan.14).
The price is also different in high season and low season. An up ride of Wannian line costs CNY65 in high season and CNY 30 in low season; a down ride coasts CNY45 in high season and CNY20 in low season. An up ride of Golden summit line is CNY65 in high season and CNY 30 in low season, a down ride costs CNY55 in high season and CNY20 in low season.