Abstract Preparation of ammonia in the laboratory used calcium hydroxide instead of sodium hydroxide, and the reasons found by experiment inquiry were: sodium hydroxide heated to molten corroding the test tube, liquid reactant flowed to the mouth of tube and the reaction rate was too fast to control. When the molar ratio of ammonium chloride and calcium hydroxide was 4:3, ammonia yield was the highest. Based on the above analysis, this paper improved the experiment used calcium oxide instead of calcium hydroxide, which could increase the ammonia yield greatly.