为深入了解激光诱导击穿光谱技术应用于钢液成分的检测机制，对45#钢样品分别为高温熔融液态和冷却凝固后的固态样品的激光诱导击穿光谱特性进行了对比分析。实验表明，相比固体样品，在相同实验条件下对钢液进行直接测量的稳定性相对较差。各波段的光谱强度液态钢的要明显强于固态钢，两者的等离子体特性存在较大差别。采用Fe的五条原子谱线用于估算两种形态样品的等离子体温度，Si的一条原子谱线 390.55 nm用于计算电子密度。结果表明，高温液态钢的等离子体温度和电子密度均高于常温固态钢，样品本身温度和形态的差异是导致两种形态样品等离子体特性和光谱特性存在差异的重要原因。

In order to deeply understand the detection mechanism of determining the components content of liquid steel using laser-induced breakdown spectroscopy, the 45# steel is used to study the different properties between liquid state and solid state which is cooled after solidification. It indicats that the direct measurement stability of liquid steel is poorer than that of the solid steel. The spectrum intensities of liquid steel are significantly stronger than those of the solid steel and the plasma characteristics of them are significantly different. Five iron atomic spectra lines are used to calculate the plasma temperature and a silicon atomic spectra line of 390.55 nm is chosen to estimate electron density. The results show that the plasma temperature and electron density of liquid steel are both stronger than those of the solid steel. The differences of temperature and physical form contribute the differences of plasma and spectral characteristics between liquid steel and solid steel.