The CaCO₃ was treated with microencapsulation, coupling agent (KR-TTS) and acrylic acid monomer to improve the adhesion of interface and dispersion of fillers in the particulated filler/polymer composite system. The physical properties of HDPE filled with surface treated CaCO₃ were measured by the mechanical, rheological and dynamic mechanical methods. And the effects of surface treatment were evaluated. In microencapsulation, it was known that formation ability and shape of microcapsules had more or less difference according to the used polymeric wall materials. ratios of formation and shape of fillers. In effects of surface treatment. mechanical and dynamic mechanical properties were improved in order of acrylic acid monomer treatment, microencapsulation and coupling agent (KR-TTS) treatment. On the other hand, rheological properties were improved in order of coupling agent treatment, microencapsulation and acrylic acid monomer treatment.