The high incidence of postpartum hypogalactia hinders the healthy development of postpartum women and the next generation. Lacquer seed oil (LSO), extracted from the seeds of the lacquer tree, has been traditionally used as a dietary supplement for promoting postpartum lactation and recovery in some districts of China. However, its physiological effects have not been verified, and the mechanism and active components of LSO have not been analyzed. Thus, we applied LSO to bromocriptine-induced postpartum hypogalactia rats. The results showed that LSO supplement effectively improves bromocriptine-induced postpartum hypogalactia. LSO also increased prolactin levels reduced by bromocriptine, promoted JAK2/STAT5 and PI3K/AKT pathways and several gene expression levels of milk synthesis in mammary gland. Moreover, metabolomic and network pharmacological analysis further revealed that JAK2/STAT5, PI3K/AKT, and estrogen signaling pathway are the potential main regulatory sites for the beneficial effects of LSO on postpartum hypogalactia, and that quercetin, kaempferol, arachidonic acid, epicatechin, and β-sitosterol are the top 5 main active ingredients of LSO. Our results suggested that LSO has great potential in the application of the improvement of postpartum hypogalactia.