The surface modification of SiC powder with KH-550 aminoorganosilanes was carried out and the optimum process parameters of modification were pointed out by using single factor experiments and orthogonal experiments. The optimum reaction temperature is 90℃, the optimum reaction time is 4h, and the optimum KH-550 concentration is 1.5g. Modified powders are characterized by using scanning electron microscopy, X-ray diffraction, infrared spectroscopy, and laser particle size analyzer. The effect of surface modification on the dispersion stabilization of SiC slurry is also analyzed. The results show that the SiC powder treated by aminoorganosilanes does not change the phase structure of original SiC; it only changes the colloidal properties in water. d_0.5 decreases slightly and particle size distribution narrows down. SEM shows that powder agglomeration is reduced and dispersion property is improved for SiC powder. Comparing with the original SiC powder, the surface characteristics of modified SiC powder occur a great change and Zeta potential increases from 17.58mV to 41mV(with pH=3.78). The dispersion stabilization of SiC slurry is remarkably increased.