Wht distance between Beijing and Rushan city?what best means to travel?

It is around 765km between by road.

Both train and long-distance bus can be fine.
By train: there is only one train operating for this journey - K411, leaving Beijing Railway Station around 22:30 and you will arrive at Rushan in around 12 hours and three quarters.

By bus: There is one bus respectively at Zhaogongkou and Lianhuachi Long-distance Bus Station. You will take sleepers on the buses and go to your destination in around 12 hours.