is there a bus from beijing to harbin?

Yes, but there is only one bus schedule from Zhaogongkou Bus Station (16:00) and Bawangfen Bus Station (17:00). The ticket fare is about CNY 310 per person.

It is actually better to take high-speed train from Main Railway Station. The train schedules are 06:58 to 15:15. The duration is 7 to 8 hours. The ticket fare of first class seat is CNY428.5 and second class seat is CNY313.5.

Hey, is there a Bus to Chengdu? How much is it? :)

Well, the distance is about 1,118 miles (1800km), and there is no direct bus to the city. You are highly recommended to take a high speed train to Chengdu from West Railway Station. The train departs at 8:30, and the duration is about 14.5 hours. You need to pay CNY 864 for a second-class seat; CNY 1,242 for a first-class seat; and CNY 2,672.5 for a business seat.

Also, there are several direct flights for this route daily and it can be the best way to go. The trip takes about 3 hours. :)