In order to further improve the performance of quick measurement of unburned carbon in fly ash by laser-induced breakdown spectroscopy (LIBS), Na2SiO3 and KNO3 are employed as binders to improve the compressibility of the fly ash powder. The fitting coefficient of calibration curve, sensitivity, measuremental accuracy, precision and limit of detection are compared between the two binders, and the performances of Si 251.61 nm and Si 288.16 nm used as the internal standards for C 247.86 nm individually are also investigated. The experimental results show that the fitting coefficient of calibration curve, measuremental accuracy, precision and limit of detection of fly ash mixed with Na2SiO3 are better than that of fly ash mixed with KNO3, and Si 251.61 nm as the internal standard for C 247.86 nm can improve the measuremental sensitivity of unburned carbon in fly ash.