Ultrafine calcium carbonate particles prepared by micro-latex method were determined by means of X-ray diffraction (XRD) and scan electron microscopy (SEM). HTPB propellants with different kinds of calcium carbonate particles were studied. They included ordinary calcium carbonate,cubic ultrafine calcium carbonate,spherical ultrafine calcium carbonate and spherical ultrafine calcium carbonate treated by emulsifying agent. The results show that shapes of ultrafine calcium carbonate particles include clava,spindle,ellipsoid,bamboo-like,sphere,arborization,coral-like,conglutinate,cube and flake. The crystal forms of ultrafine calcium carbonate particles are calcite and aragonite and particle size is less than 1 μm. The experimental condition affects the shapes of ultrafine calcium carbonate particles. The burning rates of HTPB propellant decrease by 29.6%,39.3%,46.2% and 48.6% at 7 MPa,respectively,when 3% ordinary calcium carbonate,cubic ultrafine calcium carbonate,spherical ultrafine calcium carbonate and spherical ultrafine calcium carbonate treated by emulsifying agent were added to HTPB propellant. Different kinds of calcium carbonate particles may decrease the burning rate of HTPB propellant. The burning rate of HTPB propellant with ultrafine calcium carbonate decreases more than that with ordinary calcium carbonate. Ultrafine calcium carbonate particles treated by different methods affect the burning rate of HTPB propellant little.