When choose the analytical lines of photoelectric spectral analysis, it must meet the following requirements：
1 There have a requirement of an equally between Analysis of line and the inner label line. Also it requests the close of their ionization potentials and evoked potentials. Example with Atomic line
2. When choose the Analysis line, you should pay attention to interference by other elements, try your best to be far from the overlapping interference of the other elements.
3. Choose the Analysis line which has enough concentration sensitivity, that is to say, when the sample concentration has a little tiny change, the spectral line intensity can also expressed .At the same time the analysis of line content scope should be larger, it benefit for the analysis.
4.It is better for the intensity’s zero content of Analysis line and inner line (the digital voltage value, the count) to be in the middle range of intermediate analysis content.