The invention provides a preparation technology of pure natural nanometer ultrafine calcium powder to solve the problems of easiness in introduction of impurities in the preparation process and large granularity of present calcium powders. The preparation technology of pure natural nanometer ultrafine calcium powder comprises the following steps: 1, selecting a material; 2, preprocessing; 3, cleaning ; 4, crushing; 5, calcining; 6, grinding; 7, adding water to form a uniform aqueous solution; 8, carrying out ultrasonic crushing; and 9, carrying out spray drying. The technology realizes deep processing utilization of shell substances, and a final product obtained in the invention has great market values in the fields of food safety, human body healthcare, medical health, agricultural production and environment improvement due to the unique characteristics of high penetration, sterilization bacteriostasis, pesticide degradation, acid and base balancing, heavy metal removal and mineral substance supplementation and the complete and advanced product structure.