Let B=(Ω,F,(Ft)t≥0,(Bt)t≥0,(Px)x\inRd) be the classical Brownian motion on L2(Rd,m), which is associated with a symmetric Dirichlet form (E,D(E)). For u∈D(E), ˜u(Bt)−˜u(B0)=Mut+Nut is Fukushima decomposition, where ˜u is a quasi-continuous version of u, Mut the martingale part and Nut the zero energy part. In this paper, the authors first study transformed process ˆB of B, which is determined by the supermartingale L−ut:=eM−ut−12⟨M−u⟩t, they get some properties of its transition semigroup; Then, they study the asymptotic properties of Nut, they get that if L−ut is a martingale, u is bounded and
∇u∈Kd−1, ||E.(eM−ut)||q<∞, then for every x∈Rd, limt→∞1tlogEx(eNut)=−inff∈D(E)b‖f‖L2(Rd,m)=1(E(f,f)+E(f2,u)),
where
D(E)b=D(E)∩L∞(Rd,m).