The invention relates to a composite natural preparation for lactational lambs and a milk replacer containing the composite natural preparation. The active ingredients of the composite natural preparation are prepared from the following natural plants: fructus evodiae, ficus carica, litsea cubeba, elecampane, scutellaria baicalensis, fructus forsythia, honeysuckle, rhizoma atractylodis, semen raphani, radix ophiopogonis, cyperus rotundus, hawthorn fruits, poria, medicated leaven, rhizoma pinelliae preparatum, yam and semen coicis. The 17 kinds of natural plants have the functions of invigorating stomach, cleaning bowels, regulating qi, eliminating dampness, promoting appetite, avoiding ruminal tympany, preventing diarrhea, promoting growth, and the like. Experiments prove that after lambs under a high temperature hygrothermal environment are fed with the milk replacer provided by the invention, the growth performance is not lower than or exceeds that of lambs fed by ewes, meanwhile, the health conditions of the lambs are good, and the technical level of the early ablactation of the lambs under the high temperature hygrothermal environment is improved.