To study the damage mechanism and micromachining of 6H SiC, the femtosecond (fs) laser pulse is focused on the front of the sample by a 10× microscope objective lens. The ablation pits are measured with scanning electron microscope (SEM) and optical microscope (OM). The experimental results indicate that high quality micro-structures can be fabricated in SiC crystal. Based on the dependence of ablation area on laser pulse energy, the threshold fluence is determined accurately, and the wavelength dependence of SiC ablation threshold fluence is given. The threshold fluence of SiC is found to increase with the incident laser wavelength from 0.29 J/cm2 to 0.67 J/cm2 in the visible region, while it remains almost constant (about 0.70 J/cm2) for NIR laser. For the NIR laser pulses, both photoionization and impact ionization play important role in electronic excitation, while for viaible lasers, photoionization is dominant.