The invention discloses a preparation method of paste calcium carbonate for papermaking. The preparation method comprises steps as follows: (1) qualified limestone is put into a calcinator and heated to be slaked; (2) multistage separation is performed to remove impurity particles in a calcined product; (3) the calcined product is sent into a carbonizer to be pre-carbonized for 0.5-1 hour; (4) sufficient carbon monoxide is introduced and a crystal forming agent is added till the product is thoroughly carbonized; (5) the product is dehydrated, dried and subjected to surface treatment, and paste calcium carbonate for papermaking is obtained. The preparation method has the advantages that the selection of the crystal forming agent is fitter with the whole technological process, the effect of controlling the calcium carbonate particle morphology through selection of an exact crystallization controlling agent is achieved, and the obtained final product has excellent quality, high yield, small influence on environment pollution and better technological effect.