NH₄⁺ adsorption isotherms of wormcasts obtained from earthworms fed with three different fodders in Nanning were stucied, and compared with the characteristics of those of the wormcasts from Wugong. The NH₄⁺ adsorption capacity of wormcasts was ordinarily larger than that of soils. The NH₄⁺ adsorption capacity of Nanning casts was larger than that of Wugong. The amount of NH₄⁺ adsorbed by wormcasts seemed to be related to the organic matter contained in wormcasts, espacially to the organic matter of middle temperature exothermic peak in DTA curve. The parateters of NH₄⁺ adsorption isothems of wormcasts from different fodders were different. In Langmuir equation, the constants K for NH₄⁺ adsorption isotherms of wormcasts derived from different fodders which were related to the bonding energy, were in the order of pure cattle manure > cattle manure+spoiled orange > cattle manure+residue of straw mushroom culture medium. While the parameters M，which were the adsorption maximum or total amount of solute capable of being adsorbed, were in the order of cat 1e manure-residue of straw mushroom culture medium > pure cattle manure > cattle manure+spoiled orange. The parameters b, which were indicated by the total effect of K and M, were in the order of pure cattle manure > cattle manure+spoiled orange > cattle manure+residue of straw mushroom culture medium.It is indicated that the cattle manure can not only be used as a good fodder for earthworms, but also be favorable for the high adsorption of NH₄⁺ by wormcasts, thereby forming a valuable adsorbent in soil.