The surface modification of inorganic powder is one of the important te chniques for the utilization of natural mineral resources. The paper studied the surface modification of calcite type heavy calcium carbonate (HCC) as well as its application to rubber. The samples used in the research were collected fr om weste rn Hubei and have a high purity of calcium carbonate. The techniques of both dry and wet chemical surface modification were employed in the research. The modifi cation effects of the samples were assessed by determining their active indices and sedimentary volumes. The research shows that such factors as grain sizes of the samples, pulp concentrations, types and amounts of modification agents and modification time will greatly affect the results of modification. The determ inat ion of the best conditions for the tests depended on appraising modification res ults of the products. The action of modification agent upon the surface of HCC was also studied. The result shows that the main action mode between the modifica tion agent and the surface of HCC is chemical adsorption,and the modification e ffects is excellent. The experiments of putting both modified ultra_fine HCC and light calcium carbon ate as a filler into rubber products were carried out in Wuhan Factory of Rubbe r Pro ducts. The results show that the former is more compatible with rubber.The exte nsometer and pull_apart strength of the products filled with modified HCC are ob viously higher than the products filled with light calcium carbonate, while the hardness and modulus (at a definite elongation) of the products filled with the former filler are nearly the same as those filled with the latter filler. Nevert heless, pull-apart permanent deformation of the products filled with modified HC C is larger than that of the products filled with light calcium carbonate. In sh ort, modified ultra_fine HCC, with which the rubber products show good propertie s, has a bright application prospects.