Helical drilling experiments of SiC ceramic were carried out by femtosecond laser. The effects of energy density on the processing morphology and shape of micro-hole in material were studied. The laws of variation of diameter, circularity and taper of micro-hole with laser machining parameters were analyzed. The experimental results show that micro-hole at entrance is less affected by energy density in comparison with that at exit. Higher energy density is conducive to improve the processing quality of micro-hole. Near cylindrical micro-hole of SiC ceramic with the diameter less than 250μm, the circularity more than 0.95 and the taper less than 1° was obtained. It was found that a certain degree of oxidation existed on the surface of material by detecting the machining zone. The reasons for elemental contents change in different processing areas were analyzed.