Abstract: The degradation of Robinia pseudoacacia plantation on Yellow River Delta took place in large area and the shoots of R.pseudoacacia trees were dried-up with different degree.In order to reveal the degradation causes of R.pseudoacacia plantation,soil characteristics of R.pseudoacacia plantation were studied.The results showed that soil density increased gradually with the increasing of the degradation degree of R.pseudoacacia plantation.With increasing of degradation degree of R.pseudoacacia plantation,many indices of soil nutrition were shown by decreasing degree.The contents of salt in soil increased gradually with the degradation degree increasing.It was shown that with degradation degree increasing of the R.pseudoacacia plantation the activities of soil enzymes such as peroxidase,catalase,polyphenol oxidase,urease decreased gradually.The number of total microorganism in soil of the R.pseudoacacia plantation decreased with aggravation of degradation.