The invention discloses a preparation method of special calcium carbonate for a two-component silicone sealant. The preparation method comprises the following steps: (1), adding a crystal form controlagent into a calcium hydroxide emulsion, and performing a carbonization reaction to obtain a calcium carbonate slurry; (2), adding a crystal form dispersing agent into the calcium carbonate slurry prepared in the step (1), carrying out a reaction in a dynamic mixer for 1-3 hours, and then preserving heat at 50-80 DEG C for 20-30 hours to obtain a product A for use; (3), uniformly mixing fatty acid, grease and amide according to a weight ratio of (4-8):(2-5):1, and then carrying out a reaction at 80-120 DEG C for 30-60 min to obtain a product B for use; (4), adding the product B into the product A, stirring, performing pressure filtration, drying, crushing and sieving to obtain the special calcium carbonate for the two-component silicone sealant. The calcium carbonate prepared by the preparation method provided by the invention has the BET content ranging from 21m<2>/g to 25m<2>/g, the DOP oil absorption value of 23-25ml/100g, the whiteness being greater than 95% and the consistence of12-13cm, and is a special active calcium carbonate product for the two-component silicone sealant.