What's de timetable of the direct bus from Bifeng Gorge to Chengdu?

There is no direct bus between these two places.
You need to take a city bus from Bifeng Gorge Scenic Area, and arrive at Ya'an West Gate Bus Station first. Duration is about 30 minutes.
There are many long-distance buses there that can take you to Chengdu. The schedules are from 06:30 to 19:00 with the interval of around 30 minutes.