Abstract: About 160 m high, the side slope at the left bank of Pingtou dam is nearly vertical. On the slope surface, considerable potential dangerous rock masses and partial concave rock cavity were found, as well as 35°~45°ancient landslide deposit of bulk and crushed stones and soils on the top, which was a threat. Based on technical and economical comparison between the traditional reinforcing treatment scheme and the new flexible protection network treatment scheme, the latter was used to protect the side slope. It was of the advantages such as easier construction, higher speed and less interference to the rock mass. It was of good effect, worthy reference.