Laser-induced breakdown spectroscopy (LIBS) is used to analyze the properties of boiler heating surface materials. Ovenproof steel 12Cr1MoV is made to a series of samples with different hardnesses by heat treatment process. The appropriate spectral lines of the characteristic elements are selected and the impact of different hardnesses on laser induced plasma properties of alloy steel is analyzed. Not only the relation between the hardness and the ionic to atomic spectral lines intensity ratio of a matrix element and three alloy steel elements, but also the relation between the hardness and the plasma temperature is analyzed. Experimental results show that the ionic to atomic spectral lines intensity ratio and plasma temperature increased with the increasing hardness, because the plasma shockwave characteristic and the ablation quality are different.