Laser-induced breakdown spectroscopy (LIBS) method was used to analyze steel samples. The impact of metallurgical structure on laser ablation properties of steel was analyzed. Heat-treating process was used on 45# steel to obtain three different metallurgical structures (pearlite+ferrite,bainite,and martensite). The changes of plasma temperature,electron density,and line intensity with laser energy for different metallurgical structures were analyzed. The results showed that plasma temperature,electron density,and line intensity of three different metallurgical structures had almost same tendency with the increase of laser energy. Under the same experimental conditions,the plasma temperature,electron density,and line intensity of pearlite+ferrite were the highest,those of bainite were the second and those of martensite were the lowest.