Abstract: Using digital visible spectrum analysis system, the visible spectrum line of Mg 518.36 nm in Al-based alloy sample was transformed into digitized electronic spectrum, which replaces the human visual judgment by computer automatic analysis and solves the difficult problems of spectrum recording and spectrum quantification. In this work, the digital analysis of six Al-based standard alloy samples with different content of Mg has been performed. Using spectra of Mg 518.36 nm as the analysis spectrum line, Cu 510.55 nm and Fe 510.75 nm as comparison spectrum lines separately, quantitative analysis has been made. The results indicate a proportionality relationship between the content of magnesium and the intensity ratio of the analytic and comparative spectrum lines. The development of employing digital system to guide the visual location and the spectrum identification aids in reducing the technical difficulties and improving the reliability of the quick analysis. The research results indicate that the digital technique achieves quantitative analysis and keeping the advantage of the quick analysis. Consequently, an effective solution for rapid quantitative analysis and identification in analysis of Mg in Al-based alloy is provided.