Magnesium metallic nanoparticles have been synthesized using the pulsed laser ablation in liquid media technique (PLAL) in the range of 20–30 nm by varying the laser ablation time. During the laser ablation process, the laser-induced breakdown spectroscopy (LIBS) technique is used to investigate the physicochemical properties as laser-induced Mg plasma in terms of spectral line intensities and their plasma parameters (ne and Te ). The X-ray diffraction technique and UV-visible technique show that the produced samples have a crystalline structure, and as the laser ablation time increases, the value of the absorption peak shifts to lower wavelengths and the average particle decreases, respectively. The use of the PLAL technique shows the capability to produce a metallic structure based on purging the solution by molecular nitrogen. The use of the LIBS technique shows a good and fast tool for detecting their particle sizes and the differentiation between the metallic formand its oxide structure.