K⁺ adsorption of different particle fractions of lou soil varies greatly. At certain equilibrium concentration, the sequence of the amounts of K⁺ adsorbed in different soil particle fractions is(<0.1 μm)>(<1 μm)>(1-2 gym)>(2-5 μm), the same as that of the effective cation exchange capacity of different soil particle fractions. The contribution of each particle fraction to the total amount of adsorbed K⁺ is demonstrated by adsorption contribution rate. The order of the saturated adsorption contribution rates of different particle fractions in lou soil is(<1 μm)>(1-2 μm)>(>5 μm)>(2-5 μm), and the adsorption contribution rate of clay fraction attributes to nearly 85% of the total amount. In < 1+1-2 μm,< 1+2-5 μm mixtures, the adsorption contribution rate of <1 μm increases, whereas that of 1-2 μm, 2-5 μm decreases by the power function with increasing equilibrium concentration. The adsorptive interaction of different fractions has been verified. The adsorption interaction coefficient of c, indicating that the adsorption interaction of<1 μm and 1-2 μm fractions is negative, and augments with c increment. The adsorption interaction coefficient of < 1 μm and 2-5 μm fractions is more than 1 and decreases with c increment, which indicates that the adsorption interaction of < 1 μm and 2-5 μm fractions is positive and abates with increasing c. The necessity of setting up the multi-fraction adsorption equation has been confirmed.、multi-fraction adsorption equation is q=β(c)Σr₁f₁(c).