In this paper,we prove that the weighted BMO space BMOp(ω)={f ∈ L1loc:supQ||xQ||-1Lp(ω)||(f-fQ)ω-1xQ||Lp(ω)<∞}is independent of the scale p ∈(0,∞)in sense of norm when ω∈A1.Moreover,we can replace Lp(ω)by Lp,∞(ω).As an application,we characterize this space by the boundedness of the bilinear commutators[b,T]j(j=1,2),generated by the bilinear convolution type Calderón-Zygmund operators and the symbol b,from Lp1(ω)×LP2(ω)to Lp(ω1-p)with 1<p1,p2<∞ and 1/p=1/p1+1/p2.Thus we answer the open problem proposed by Chaffee affirmatively.