The corrosion inhibition behavior of Mg-8Li-3Al alloy in NaCl solution with sodium dodecyl sulfate (SDS) was investigated by hydrogen analysis, scanning electron microscopy (SEM), electrochemical test, scanning Kelvin probe force microscopy (SKPFM) and computational methods. Results showed that the corrosion resistance of Mg-8Li-3Al alloy in NaCl solution was effectively improved with SDS. The SEM and SKPFM results confirmed a dense, 200 nm-thick SDS-adsorbed layer had formed on the alloy surface. The separation energy ∆E_gap and adsorption energy E_ads of SDS on the Mg surface were calculated by density functional theory and molecular dynamics simulations, respectively. And the corrosion inhibition mechanism was hypothesized and described.