The pitch was dried and modified with 1 mass% nickel nitrate and 10 mass% Si powder successively, then carbonized in Ar atmosphere at 900, 1000, 1100, 1200, 1300, and 1400℃, respectively. Effects of carbonization temperature on phase composition and microstructure of Ni-catalyzed silicon modified pitch were studied by XRD, FESEM and EDS, and the growth mechanism of SiC whisker was discussed as well. The results show that SiC whisker forms in the carbonized products of modified pitch processed in Ar atmosphere at 1000, 1100, 1200, 1300, or 1400℃; its length is about 1 to 6 μm; its growth mode is apical growth, and its growth mechanism accords with V-L-S mechanism.