Abstract: In this paper,the theoretical foundation of mode clarification is introduced at first,based on which the analysis is done according to the results got by the Back-Propagation neural(BPN)new training. It is found that the features of the sedi ment capacity ability are similar to the hyper-concentration and lower-concentration flow. So the sediment capacity ability is not a desirable criterion for the classification of hyper concentration and lower-concentration flow. This agrees well with the results got by other researchers. During the BPN training,if,in most cases,the Bingham shear stress of the flow is greater or less than certain critical value,the training results always agree well with the measured data,while others not Several training tests get nearly the same conclusions. It can be deduced that there indeed exists a critical value of the Bingham shear stress, and when the shear stress exceeds this critical value,the flow can be classified as the hyper concentration flow. For the flow with a hyper-concentration powered phenolic,this critical value is about 3.2×10^-1Pa.