Laser-induced breakdown spectroscopy (LIBS) is used to analyze unburned carbon in fly ash. The samples are obtained by using fast ashing method. In the experiment,the carbon line at 247.86 nm presents strong interference by iron line at 247.95 nm,which affectes the analysis of unburned carbon by using LIBS. Without strong interference of other lines,the carbon line at 193.03 nm in deep UV is used,and calibration curve is constructed. The analysis results show that C 193.03 nm line can be detected at atmospheric pressure by using spectral detection system with deep UV detector coating,short focal length collimating lens and anti-UV fiber. The correlation coefficient of calibration curve is 0.99,and the detection of limit of unburned carbon is 0.74% (mass fraction).