Abstract:`Zea mays cv. Luyu 14‘ was used to study the effects of Ca2+ on stomatal conductance, net photosynthetic rates, Mehler reactions and the activities of the antioxidant enzymes, SOD and APX, under NaCl stress. Additions of 2-16 mmol·L－1 Ca2+ suppressed stomatal conductance of maize leaves under normal growing conditions but significantly increased stomatal conductance under NaCl stress. Mehler reaction dependent electron transport rate was increased by the addition of 2－8 mmol·L－1 Ca2+ both in controls and in the NaCl stressed maize leaves; however, the extent of the increase was greater in salt stressed maize leaves. The total electron transport rate was reduced in controls but increased in NaCl stressed maize leaves by the addition of 2－8 mmol·L－1 Ca2+. The addition of 8 mmol·L－1 Ca2+ significantly increased the activities of SOD and APX with the extent of the increase greater in APX than SOD. In conclusion, addition of Ca2+ alleviated inhibition induced by NaCl stress in maize leaves, which was associated with the promotion of photosynthesis, the enhancement of Mehler reaction, and the activities of antioxidant enzymes. The enhanced Mehler reaction could not only consume excess excitation energy to avoid over reduction of the electron chain of photosynthesis but also promoted xanthophyll cycle dependent thermal dissipation by forming a transthylakoid membrane pH gradient (ΔpH) to efficiently protect maize leaves against photodamage under salt stress. Also, the active oxygen produced via the Mehler reaction was scavenged by the enhanced anti-oxidative enzymes.