The production cost will be greatly reduced if nitrogen can be used instead of inert gas in the spray forming process of magnesium alloys,but the heat from the reaction between magnesium alloys and nitrogen makes magnesium alloy burn easily.To solve the problem above,the ignition point of Mg-Ca alloy under nitrogen atmosphere was studied using a home-made experimental device and DSC-DTA.Results show that under nitrogen atmosphere,Ca addition has a great effect on the ignition point of Mg alloy.The ignition point of the Mg-5Ca bulk even exceeds 1,030 ℃,and the alloy can be held for 30 min at 900℃ without burning; while the average ignition point of Mg-5Ca powders is lower than 700℃,and it increases with the increasing particle size.Moreover,the purity of nitrogen must be in a certain scope; Mg-Ca alloy shows a higher ignition point under nitrogen with a purity of 99.5％.Based on the experimental results,the best adding content of Ca and the purity of nitrogen were determined,and the security and economic performance of preparing magnesium alloys by spray deposition were improved with nitrogen as atomizing gas.