Biomedical research indicates that human gait is considerable different when walking on different terrain. In this paper, terrain identification scheme for an intelligent bionic leg (IBL) is presented. Terrain identification system is modeled by the procedure neural networks (PNNs) and is used to identify the current terrain type based on the ground reaction force (GRF) information. According to identification result, damping moment of magneto-rheological (MR) damper mounted on knee joint of IBL is adjusted to accommodate changing conditions. This paper presents the PNNs model and calculates the related arithmetics. Terrain identification results prove the rationality and feasibility of the proposed scheme.