The invention discloses a production technique of nano calcium carbonate by a normal temperature method, belonging to the technical field of fine chemical engineering. The production technique comprises the following steps: proportioning, carbonizing, treating, dehydrating, primary drying, secondary drying and depolymerizing. The invention has the characteristics of low equipment investment, low energy consumption, low production cost and the like, can implement production under normal temperature conditions, and can control the particle size and crystal form. The nano calcium carbonate produced by the technique disclosed by the invention can be used as a filling material in plastics industry, rubber industry, paint industry, paper manufacturing industry, ink industry, adhesive industry and other industries.