In order to prevent the collapse of embankment, the concrete-block,vegetation and polymer sheets are used to cover the slope face. Polymers are used for protection of slope face from erosion and seepage occurring inside the embankment. We developed a polymeric waterproof and antiweed sheet made of complex materials with high performances, using a newly developed estimation method. This sheet has enough stability against weed penetraiton, abrasion wear, alkali solution, UV rays and so on. In this paper, we describe our estimation method and newly developed waterproof and antiweed sheet.