The work aims to evaluate the effect of ambient relative humidity on qualities of corrugated carton. The performance indicators such as compressive strength, bursting strength and moisture absorption rate of the 3-layer, 5-layer and 7-layer corrugated cartons were compared at 23 ℃ and the relative humidity of 50%, 70% and 98%, respectively. The moisture absorption rate and moisture content of the corrugated cartons were enhanced with the increase in the ambient humidity. The bursting strength, edge compressive strength, compressive strength and other performances of the corrugated carton remained stable when the ambient relative humidity was 50%~70%. When the relative humidity reached to 98%, the bursting strengths of the 3-layer, 5-layer and 7-layer corrugated cartons at the relative humidity of 50% were respectively reduced by 53.8%, 74.1% and 76.3%; and the edge compressive strengths were reduced by 71.4%, 70.3% and 77.5%, respectively. The compressive strength and stacking layers were significantly reduced. The moisture resistance and pressure resistance of the 7-layer corrugated carton were better than those of the 3-layer and 5-layer corrugated cartons. High humidity can cause significantly reduced performance indicators and damaged functions of the corrugated carton.