Abstract: After foliar application with 10 mmol·L^-1 CaCl₂ each day for the first week,Kosteletzkya virginica seedlings were moved into an incubator,kept at 40 ℃ and monitored periodically for related physiological indices.Results show that Ca²⁺ could lower contents of proline and soluble sugar,prevent seedlings from withering and decreasing in root activity.Besides,Ca²⁺ could inhibit the increase of membrane permeability,improve the activity of Ca²⁺-ATPase.Thus,Ca²⁺ improves the tolerance of K.virginica seedlings to heat.