Abstract: The present invention relates to a calcium carbonate having a surface charge, the preparing process thereof and filler for producing a paper using the same. The present invention provides the process of preparing a calcium carbonate having a surface charge, characterized in that it comprises the following steps of: preparing a solution mixture of one or more monomer selected from the group consisting of calcium hydroxide, acrylic acid, acrylamide, or [2-(acryloyloxy)ethyl]-trimethylammonium chloride; removing dissolved gases such as oxygen and carbon dioxide in the said solution by injecting nitrogen (N2) gas; adjusting pH of the said solution; and inducing a reaction by adding polymerization initiator of a high molecule while injecting carbon dioxide to the said mixture.