For highly efficient processing technology of hard and brittle material such as SiC/SiC composites, laser machining has always been the focus of current research. In this work, the effect of composites density on the nanosecond pulse laser machining behaviors was systemically studied. The results revealed that the composites density will largely affect the morphology of laser machining, especially for the micro-hole inlet ablation condition and outlet circle degree. Besides, the roughness of the cutting surface is highly related with density, while the generated oxides and melting substances making the cutting surface smoother in high density samples. Finally, the laser machining induced products exhibited less relationship with density but high relationship with machining time. This paper provides a clear image that how intrinsic properties affects the laser machining behaviors and processing quality.