How can I get from Shanghai to huangshan scenic spot by one direct bus?

You can take coach from the South Bus Station and arrive at the scenic area directly. The bus schedules are 06:37, 07:57, 09:07, 10:27 and 14:39. The ticket fare is CNY 148 per person.
In addition, you can buy the tickets when you arriving at the bus station. :)

Thank you so much for your reply. I've booked the bus ticket. However I am unable to book the return ticket from huangshan. The lady at the ticket office said I have to book from huangshan. However we need to get back by Sunday night as hubby has work the next morning.. And I don't want to risk it incase we can't find return tickets.pleade advise.

Yes, the staff of the bus station is correct. You need to buy the return ticket at Huangshan.
I see. You can buy them when you arriving at Huangshan Bus Station first. Then go to the scenic area. After touring around, you can hold the tickets to take the coach and go back to SH.
If you still cannot buy the tickets, you still can hire a private car to go back. The weak point is that the fare would be a little bit expensive.
So there is always a way to solve the problem. Don't worry. Please fully enjoy your journey!