Abstract: Based on the method of the grey connected analysis in the grey system theory, the author analysed the relation among the height, diameter of black locust and the main chemical factors of soil: HCO3-, C-~, SO24-, Ca2+ Mg2+, K++Na+, the total amount of anion, saliferous amount of soil and pH value. The order of arrangment of chemical factors is as follows according to their connected degrees (l)on the height of tree: pH, SO24-, HCO3-, Mg2 + , Ca2 + , the total amount of anion, Na++K+, Cl~, saliferous amount of soil} <2)玭 the diameter of tree. pH, SO24-, HCO3-, Mg2+ , Ca2+ the total amount of anion, CI-, Ma+ + K+, saliferous amount of soil. The results show that pH value is the most important chemical factor of soil which can influence the growth of middle aged forest of black locust on the sea shore, but not the salt amount of soil. Our research effects can be used as a theory for soil amendment and improvement of the quality of afforestation on the sea shore.