The present invention provides peppermint composite cellulose fibers, which contain 1-12 wt% of a peppermint extract component and 0.5-3 wt% of peppermint odor essential oil slow-release microcapsules, wherein the dry breaking strength of the fibers is 1.0-3.0 cN/dtex, the wet breaking strength of the fibers is 0.8-1.6 cN/dtex, the dry elongation at break is 16-24%, the residual sulfur content is less than or equal to 18 mg/100 g, the antibacterial activity logarithm value is more than 2.0, and the bactericidal activity logarithm value is more than 0. The peppermint composite cellulose fiber preparation method comprises: peppermint extract adding liquid preparation, degenerated viscose glue preparing, peppermint blending viscose glue preparing, spinning and post-treating, and filament drafting and post-treating so as to obtain the peppermint composite cellulose fibers. The peppermint composite cellulose fibers of the present invention have characteristics of good wearability, textile processability, antibacterial function, bacterial inhibition function, lasting and fresh peppermint aroma, lasting odor, good textile processing performance, and significant antibacterial function.