In order to improve detection sensitivity of Cu element in sewage by laser induced breakdown spectroscopy (LIBS). The LIBS test in aqueous solution of cuprum are conducted with a direct blow to the liquid level and the filter paper enriched method, experimental parameters are optimized and results of different methods are discussed. The results show that the best analyzing spectral lines of Cu is 324.7 nm; the optimal delay time is 1400 ns; the optimal pulse laser energy is 100 mJ. Getting the calibration curve of two methods, the correlation coefficients are 0.97047 and 0.99901. The limit of detection are 74 μg/mL and 1.5 μg/mL respectively. The results show that filter paper enrichment method works better. This study indicates that filter paper enriching method can improve the sensitivity of detection and reduce the limit of detection.