The invention discloses a synbiotic feed additive for pregnancy sows. The synbiotic feed additive is prepared from a composite probiotic agent, maltodextrin, isomaltooligosacharide, glucose, citric acid, complex vitamins, radix astragali, honeysuckle flowers, bighead atractylodes rhizomes, rhizoma atractylodis, cortex magnoliae officinalis, katsumada galangal seeds, Chinese mugwort, semen cuscutae, Chinese taxillus herb and crispateleaf ardisia roots, wherein the composite probiotic agent is a mixture of enterococcus faecium, microzymes, bacillus subtilis and bacillus coagulans. The inventionfurther provides an application method of the additive. During period of pregnancy of sows, the feed additive is added to feeds according to the addition quantity that the added feed additive is 0.3-5% of the weight of the pregnancy sows for feeding. The feed additive has the efficacy of preventing miscarriage, promoting delivery, nourishing the liver, supplementing qi, resisting bacteria, diminishing inflammation, being nutritive and health-care and the like, is free from toxic and side effects, and can be used as a feed additive to be added to a feed for the pregnancy sows for feeding. The feed additive can improve the constitutions of the pregnancy sows in essence, the immunity and the stress resistance of the pregnancy sows can be improved, the spontaneous delivery rate of the sows canbe greatly increased, and improving of quality of piglets produced by the sows can be facilitated.