The laser-induced breakdown spectroscopy (LIBS) based on the C element is investigated by the spectroscopic imaging and plasma monitoring techniques, and the ablation quality and repeated heating of the sample are studied in depth. The research results show that the spectral intensities of the C element under single and double pulse LIBS are obviously different. The double pusle signal enhancement is not only attributed to the increase of the ablation mass, but the change of plasma forming environment caused by the physical change of the double-pulse signal reheating.