The compression strength of corrugated box under different humidity is investigated by experiments and finite element method with an orthotropic plate theory, and the load-deformation curve and compression strength of corrugated box are obtained. The compression strength of corrugated box is exponentially decreased with the increasing of the relative humidity. The results from finite element method are consistent with the experiments, and the finite element method with orthotropic plate theory can be effectively used to analyze the deformation and compression strength of corrugated box.