A novel biomimetic surface modification method utilizing mussel-inspired chemistry was used to prepare tungsten disulfide (WS2) nanocomposites, which enhanced the dispersion stability and tribological performance of WS2 in polyalkylene glycol (PAG). Herein, WS2- polydopaminemethoxypolyethylene glycol amine (WS2-PDA-MPGA) was first synthesized via mussel-inspired chemistry and used as a lubricant additive in PAG. After modification, the dispersion stability of WS2 nanosheets in PAG was obviously improved. Moreover, the tribological performance of WS2-PDA-MPGA in PAG at high temperature was evaluated by the oscillating reciprocating tribometer. Compared to pure PAG, the lubricant composition containing WS2-PDA-MPGA exhibited excellent performance in friction reduction and anti-wear properties at high temperature. The optimal tribological performance could be obtained when the percentage of additives was 0.9 wt%. The tribological results indicate that WS2-PDA-MPGA, with its good dispersion stability, has better friction reduction and anti-wear properties than does WS2 in PAG base oil. The chemical composition analysis of the wear surface indicated that a stable protective film had been formed by physical adsorption and tribo-chemical reactions. Therefore, the surface modification strategy is an effective way to improve the dispersion stability of WS2 in PAG, which can be expanded application of WS2 in the tribological field.