In order to study the detection sensitivity of Na elements in water, the Na elements in NaCl solution were detected by laser induced breakdown spectroscopy. Choosing NaⅠ589.0 nm and NaⅠ589.6 nm as analytical spectral lines, we used the NaCl solution with 6 kinds of concentration and adopted external standard method, internal standard method and wavelet transformation noise reduction method to present NaCl solution Na element calibration curve, finding that the linear correlation coefficient r of calibration curve obtained by using internal standard method is 0.998, better than that of calibration curve obtained by using external standard method (r=0.985), and is superior to the external standard method after wavelet noise reduction (r=0.986). In contrast, the wavelet transformation reduced the RSD from 5.68% to 1.61%, thereby reducing the LOD value from 50.8 to 19.54 μg·mL-1. The internal standard method selects the NaⅠ589.0 nm and NaⅠ589.6 nm sodium atomic line and the internal standard reference line HⅠ656.2 nm hydrogen atom line intensity ratio can effectively overcome the impact of experimental conditions fluctuations, therefore, the linear correlation coefficient of the calibration curve of Na element in NaCl solution obtained by using the internal standard method is the largest. For the wavelet transformation noise reduction processing method, the noise caused by the continuous background of the LIBS spectrum can be effectively reduced, and the influence of the experimental condition fluctuation on the LIBS spectral information cannot be overcome. Therefore, the wavelet variation noise reduction method can improve the RSD of the LIBS, but has little effect on -the improvement of the linear correlation coefficient of the calibration curve given by the external standard method after noise processing. It is indicated that the internal standard method effectively improves the detection sensitivity and reduces the influence of fluctuations in experimental conditions. The calibration curve has a better linear correlation. The wavelet transformation noise reduction process effectively reduces the continuous background spectral noise in the LIBS spectrum, and the LIBS detection limit becomes lower. The RSD and LOD values obtained by analyzing the line of NaⅠ589.0 nm are smaller than those of the line with the line NaⅠ589.6 nm. The upper levels of the two lines of NaⅠ589.0 nm and NaⅠ589.6 nm are 2.104 and 2.102 eV respectively. It was found that the upper level of the analytical line has an effect on the RSD and LOD values of the Na element in the NaCl solution, and the upper level is large, while the RSD and LOD values are small. The results of this study showed that LIBS technology can realize rapid detection of heavy metal elements in solution, and has potential application prospect in environmental water pollution detection.