The invention discloses a method for wet modifying of ultra fine calcium carbonate, and the method comprises the following steps: pulverizing; milling by a micro-powder milling machine; wet grinding,adding of modified bagasse slurry; sieving; and drying. The method can well improve the dispersing property of the calcium carbonate, prevents agglomeration during the grinding and drying process, andat the same time helps to improve the toughness of a downstream product-paper to some extent.