I was on B1 Visa in past two years. Now I am coming to US for long term assignment in which I will get US salary. I want to know whether my preview B1 stays can be added in this year’s total stays calculation or not?

The B-1 visa time IS considered in determining Substantial Presence, but only on a pro-rated basis. You count one day in three for 2008 and one day in six for 2007.

As implied by ATE, you would count full days for 2009.