Abstract: The present invention provides feed additive to promote the growth of sows and piglets, which comprises serine, astragalus and ginseng leaves. The feed additive preferably contains: 50-60 wt % of the serine, 20-25 wt % of the astragalus, 20-25 wt % of the ginseng leaves and the balance of rice bran meal as a carrier. The invention also provides applications of the above-mentioned feed additive in promoting the growth of sows and piglets, that is, before feeding, make the serine content in the diet reach 0.69 wt % and incorporate it into the diet of gestational sows, and/or make the serine content in the diet reach 0.82 wt % and incorporate it into the diet of lactating sows.