A new earth-abundant element material Cu2MgSnS4 was synthesized by hot-injection methods. X-ray diffraction, Raman spectroscopy, and transmission electron microscopy elucidated that as-prepared nanoparticles are Kesterite Cu2MgSnS4 without binary compounds coexisting. Scanning transmission electron microscopy-energy-dispersive spectroscopy element mapping shows the copper, magnesium, tin, and sulfur elements distributed uniformly in the nanoparticles. The result of the UV-vis absorption spectra revealed that the Cu2MgSnS4 nanoparticles have an optical band gap of 1.63 eV, which is suitable for application in the field of photovoltaic cells.