The Hitchin-Simpson equations are first order non-linear equations for a pair of connection and a Higgs field, which is closely related to the Higgs bundle theory over Kähler manifold. In this paper, we study the behavior of sequences of solutions to the Hitchin-Simpson equations over closed Kähler manifold with unbounded L 2 norms of the Higgs fields. We prove a compactness result for the connections and renormalized Higgs fields.As an application, we study the realization problem of Taubes' Z2 harmonic 1-form over closed Kähler manifold. Using the Hitchin morphism for SL(2, C) Higgs bundle, we give a necessary and sufficient condition that whether a Z2 harmonic 1-form can be realized by a sequence of solutions to the Hitchin-Simpson equations.