The paper deals with the genetic characteristics of lime concretion black soil and albic soil in North Jiangsu Plain, the features of association of the soils and their relation to ecological environment. This work was made through studying formation of lime and Fe-Mn concretions in the two soils. The results showed that the genesis of the two soils were deeply influenced by ancient ecological environment. It was a common characteristic of the two soils that periodical alternation of oxidation-reduction resulted in the leaching of Fe and Mn and the formation of Fe-Mn concretions. The formation mechanism of the small Fe-Mn concretions (less than 2-3 mm) was different from that of large ones(greater than 5-7 mm). Lime concretions originated from the ground water were the result of regional geochemical sediutenration. So, they occured not only in the two soils but also in the buried palesols of the Quaterary deposits in the region. Finally, the soil association existed in this region was affected by both recent and ancient enmronments.