In　situ　Mg　isotope　analysis　of　geological　materials　by　laser　ablation　multiple　collector-inductively　coupled　plasma　mass　spectrometry　(LA-MC-ICP-MS)　is　a　powerful　tracer　technique　for　tracking　geological　processes.　In　Mg　isotopic　analysis　by　LA-MC-ICP-MS,　medium　or　high　mass　resolution　was　commonly　applied　to　avoid　spectral　interferences.　However,　the　improved　mass　resolution　can　result　in　reduced　intensity　and　an　aggravated　matrix　effect.　In　this　study,　the　analytical　results　demonstrated　that　the　main　interferences　((CN+)-C-12-N-14　and　Ca-48(2+))　in　Mg　isotopic　analysis　can　be　significantly　suppressed,　and　the　matrix　effect　can　be　significantly　reduced　with　water　added　after　the　laser　ablation　cell　(i.e.,　wet　condition　or　wet　plasma)　using　fs-LA-MC-ICP-MS.　Thus,　accurate　and　precise　Mg　isotopic　composition　can　be　achieved　with　low　mass　resolution　and　the　non-matrix-matched　calibration　method　by　fs-LA-MC-ICP-MS.　The　applicability　of　the　combination　of　low　mass　resolution　and　wet　plasma　was　systematically　evaluated　by　the　assessment　of　the　interferences,　the　Mg　three-isotope　plot,　instrumental　long-term　reproducibility　and　the　intensity　mismatch　effect.　Applying　the　optimized　method,　accurate　and　precise　Mg　isotopic　compositions　in　silicate　reference　materials　with　various　matrices　can　be　achieved.