Nano-sized calcium carbonate was prepared by carbonization method.In the process of reaction,the initial reaction temperature was adjusted to synthesize nano-sized calcium carbonate with different crystal sizes.The phase,morphology and particle size of calcium carbonate were analyzed by transmission electron microscope（TEM） and laser particle size analyzer.The modified nano-sized calcium carbonate was applied to the preparation and extrudability of silicone sealant base material. The effects of particle size,dispersibility,rheology and surface modifier on extrudability of modified nano-sized calcium car-bonate were analyzed.The results indicated that the particle size was in the range of 50~90 nm,the yield value was in the range of 66.4~148.9 Pa and the viscosity was in the range of 0.5~0.75 mPa·s,the nano-sized calcium carbonate compounded and modified by sodium stearate and two kinds of low molecular weight fatty acid coating agents（LH-2 and LH-3） showed good extrudability for silicone sealant base material.