The invention relates to a preparation method and application of a multifunctional health-care porous elastic big-belly yarn. The multifunctional health-care porous elastic big-belly yarn is prepared from two core yarns, two fixed yarns and a decorative yarn, wherein the fixed yarns are core-spun yarns obtained by carrying out blended processing on silver fibers, copper fibers, soft silk fibers and DOW-XLA elastic fibers; the core yarns are blended hollow yarns obtained by carrying out blended processing on Porel fibers, hollow polyester fibers and provilion; the decorative yarn is a blended rough yarn obtained by carrying out blended processing on nettle fibers, apocynum fibers and alpaca wool fibers. The multifunctional health-care porous elastic big-belly yarn not only has a special form, but also is rich in yarn colors, multiple in shapes and ever-changing; products developed by using the multifunctional health-care porous elastic big-belly yarns are natural and environment-friendly, have the health care functions of resisting bacteria and eliminating inflammation, protecting skin and keeping fitness, absorbing moisture and releasing sweat, deodorizing and resisting aging, and the like, are good in comfortableness, and do not cause adverse effects when being contacted with a human body; the multifunctional health-care porous elastic big-belly yarn is mainly used for various textiles such as yarn-dyed female lines, knitted fabrics, tweed, coarse worsted fabrics, decorative articles, hand knitted fabrics and shawls.