Back propagation neural network technique has been applied to many areas due to itspowerful capacity of learning and achieved good results. When there is no known samples for learning,the technique can not be applied successfully. The paper applied the self--organizing neural network toidentify automatically lithology from log data. The method was applied to Songliao basin and it is verified by comparing with the known lithology column in some real wells that the technique is successful for lithology identi...