A new kind of composite filler was prepared by coating the carrier of calcium carbonate,with titanium dioxide via the mechanochemical method. Then,the structure of the composite filler was characterized by using such parameters as oil-absorbed values,hiding power and particle size and by means of FT-IR and SEM,and the properties of the composite filler and its effect on paper were then investigated. The results show that( 1) the particle size of the composite filler is larger than the uncoated calcium carbonate; ( 2) the chemical bonds form between calcium carbonate and titanium dioxide and is of a good strength; ( 3) the hiding power and the oil absorption values of the composite filler are close to those of titanium dioxide; and( 4) at the same ash content,the optical properties and the physical strength of the paper filling with the composite filler are close to those of the paper filling with titanium dioxide,thus the composite filler being able to partly or wholly replace titanium dioxide.