In view of the evaluation question of the non-woven clogging index,this paper studies the permeation criterion and the gradient ratio criteria about the clogging index of the nonwoven geotextile commonly used in the slope filter layer of the channel regulation project,and finds out the relationship between the two points:the hydraulic gradient of the standard drainage gradient and gradient ratio limit.Based on this combination point,this paper carries out a series of non-woven clogging tests,and explores the evaluation model of non-woven clogging index to fit the evaluation formula of the non-woven clogging index in the anti-filtration layer of the bank slope and guide the calculation of the time period for non-woven fabric to function properly.The results fill the gaps in the field of research,lay the foundation for the study in this field,and have important value and significance for the future to promote the study of the field.