利用激光诱导击穿掺杂Cr、Cu 元素的自制土壤样品，对元素特征谱线的信背比随含量的变化情况进行对比分析，并选择常用谱线Cr(I) 425.435 nm，427.481 nm、Cu(I) 324.754 nm，327.396 nm，利用相应Fe 谱线作为内标作出校准曲线，计算检出限，研究谱线跃迁能级的原子组态、角动量和跃迁几率等微观特性对校准曲线和检出限的影响。研究结果表明，信背比高的谱线得到的检出限相对较低，对元素检测更为敏感；谱线的信背比与谱线对应的跃迁几率无关。跃迁原子组态相同的谱线的信背比随含量变化显示出相同的变化趋势，其中角动量相对较大的谱线Cr(I)425.435 nm(4-3)和Cu(I) 324.754 nm(3/2-1/2)激发状况较好，得到的校准曲线的线性拟合值也相对较高，检出限相比于角动量小的谱线Cr(I) 427.481 nm(3-3)和Cu(I) 327.396 nm(1/2-1/2)分别降低了11%和42%，对元素检测的灵敏度更高，更适合作为元素检测的特征谱线。

Laser is focused on soil samples doped with Cr and Cu elements. Signal-to-background ratio (SBR) of Cr (I) 425.435 nm, 427.481 nm and Cu (I) 324.754 nm, 327.396 nm is analyzed. The calibration curve is drawn using the intensity ratio of each line to the Fe reference line intensity, and the limit of detection is calculated. The effect of atomic configuration, angular momentum and transition probability on calibration curve and limit of detection is studied. It is indicated that the high SBR spectral line gets lower limit of detection, and is more sensitive to element detection. The spectral line SBR is independent on transition probability. The variation in SBR with element content exhibits similar characteristics for the lines with the same atomic configuration. The excitation of lines with large angular momentum is better with higher regression coefficient of calibration curves. The limit of detection of Cr (I) 425.435 nm (4-3) and Cu (I) 324.754 nm (3/2-1/2) decreases by 11% and 42% compared to the lines Cr (I) 427.481 nm (3-3) and Cu (I) 327.396 nm (1/2-1/2) respectively. The lines with large angular momentum are more sensitive and more suitable for element detection.