A set of experimental measuring devices is developed by combining the laser ablation technique with absorption spectroscopy to obtain laser ablation absorption spectra. Alloy steel is used as the test sample, and the ground state transition (394.40 nm) of the aluminum atoms is selected as the analytical spectral line for the quantitative detection and analysis experiment of aluminum in the alloy steel samples. The experimental results reveal that the most suitable experimental conditions for the successful detection and analysis of aluminum include a laser pulse energy of 30 mJ, a detection height of 2 mm, and a sampling delay time of 8 μs. Under these optimized conditions, the high-resolution and high-sensitivity absorption spectrum signals of the aluminum atoms in the alloy steel standard samples are obtained, while the calibration curve of the aluminum content and absorption intensity are also determined. Moreover, the fitting parameters of the calibration curve are higher than 0.999, and the limit of detection is 0.066%. Thus, laser ablation absorption spectroscopy proves to be effective for the quantitative analysis of aluminum in alloy steel, while the results also indicate its great potential for the quantitative analysis of trace elements and isotopes in alloy steel and other materials.