In this paper we consider the spectral properties of periodic elliptic operator ∑dj,l=1Djw(x)ajlDl+V(x) in Rd, d ≥ 3, where A=(ajl) is a d×d positive definite matrix with real constant entries, V(x) and w(x) are periodic scalar function with respect to the same lattice, and w({x) is positive. Using a new uniform Sobolev inequalities on the d-torus established in [22], we prove that the spectrum of the operator is purely absolutely continuous if Lloc2pd/d+2p(Rd) and w ∈ ∧1+αp, ∞(Td)∩L∞(Td) for some α>0, p≥ d, or V ∈ L loc2d/3(Rd), w ∈ C1(Td), or V ∈ Llocd/2(Rd), w ∈ L2, locd/2(Td).