The invention provides a preparation method of ultra-dispersed functional calcium carbonate, and belongs to the technical field of nano material preparation, the preparation method comprises the following steps: carrying out digestion reaction on calcium oxide and water, carrying out magnetic separation enrichment on the obtained slurry through a magnetic separator, collecting the outflow calcium hydroxide slurry, and carrying out aging reaction, sieving and water addition dilution to prepare a calcium hydroxide suspension; 2-amino-2-methyl propanol is added into the calcium hydroxide suspension, carbon dioxide gas is introduced for a carbonization reaction, when the pH value of a reaction system is reduced to 6.5-7.0, the carbonization reaction is stopped, and obtained calcium carbonate slurry is dehydrated, dried, smashed and screened to obtain the ultra-dispersed functional calcium carbonate. The cubic ultra-dispersed functional calcium carbonate is prepared by adding the 2-amino-2-methyl propanol, and the cubic ultra-dispersed functional calcium carbonate is large in specific surface area, good in dispersity, not prone to agglomeration and low in oil absorption value.