is there any sight seeing bus operators in qingdao city and how is the cost?

Yes, the sightseeing bus in this city totally has four routes.

For route No.1, the single trip ticket fare is CNY 10 per person.
For route No.2, 3, 4, it costs CNY 15 per person per time. And the through ticket costs CNY 30 per person. (The through ticket means that you can take this sightseeing bus for unlimited times in 24 hours).

How and where to buy the sightseeing tickets?

You can buy the ticket while getting onboard. There is someone handling it, no worry.

Where can I abroad siteseeing bus? where does it go?
which attractions?

The bus goes by Zhanqiao, Luxun Park, Nanhai Road, Badaguan Scenic Area, Erliao, Wusi Square, Polar Ocean World, Sculpture Park, Shilaoren, Shazikou, Dahedong Parking Lot etc. You can buy tickets and board the bus from any of the spots. :)