The present paper deals mainly with the changes of thermoynamic parameters in the exchange of Zn-Ca of several typical soils. 50 ml solution containning Zn (10-200 ppm) was added to 2.50 g soils saturated by Ca, and then put in plastic container (vessel) and shaken occasionlly, standing under 20℃ and 50℃ for 72 hrs and then centrifuga,lized. The Zn and Ca in samples were determi.ne:d by Plasme Spectrometray. The results obtained showed that the selectisity coefficients (K_c) of the soils. was in the following order: Yellow browu earth>Red earth≥Latosol. K_c was decreasing with the increase of the saturation percentage for Zn on solid. It is considered from Fig. 1 that there are two adsoption sites with different energy on the solid surface, one has a stronger and another has a weaker affinity to Zn⁺⁺. In the process of Zn-Ca exchange, the effect of △H⁰ on △G⁰ was much more than that on the △S⁰, which was especially evident for Yellow brown-earth. It is.found from the changes of the theromodyuamical parameters that Yellow brown earths had a higher preference for Zn⁺⁺ and a tighter banding with Zn⁺⁺ than Red earths and Latosols,which is related with the differences in types and properteis of clay minerals.