The invention provides an immune stimulant used for improving the immunity function of piglets. The immune stimulant comprises the following raw materials: astragalus membranaceus, rhizoma atractylodis macrocephalae, angelica sinensis, fructus lycii, liriope spicata, dendrobe, fructus ziziphi jujubae, cortex mori, caulis spatholobi, turmeric, cacumen biotae, fructus gardeniae, cordate houttuynia, sweet wormwood, cyperus rotundus, resurrection lily rhizome, assorted Chinese herbal tea, fennel, myristica fragrans, walnut kernel, semen raphani and sapanwood. The immune stimulant has the advantages of rich resources, low toxicity, economy, environmental protection and the like, can improve feed conversion ratio, improves immunity and prevents diseases.