Four kinds of samples (graphite, CaCO3, NH2C6H4SO3H and coal) with different forms of carbon are used for laser-induced breakdown spectroscopy (LIBS) experiment. Different gases (air, nitrogen, argon) are used to analyze the influence of gases on atomic emission spectrum and molecular emission spectrum for carbon materials to study the LIBS properties for the carbon materials with different forms. The results show that the variation rules of neutral atomic emission C I intensities are that the strongest is in argon, the medium is in air and weakest in nitrogen. Since there are reversible reactions among molecular emission C2, N2 and CN, the variation rules of molecular emission C2 and CN depend on not only whether the samples themselves contain C-C, C=C or C-N, but also the interaction mechanism between the plasma and surrounding environment.