 Ankle rehabilitation training becomes a tough question for the patients with ankle joint injuries especially with the hemiplegia after stroke. Here a novel powered ankle foot orthoses which can provide ankle dorsiflexion and plantar flexion assistant using electric motor is proposed in this paper. The mechanical structure of the orthoses includes wearing parts, ankle joint hinged part, driving unit, transmission mechanism and sensing units. This study provides a new method for ankle foot orthoses design and has great significance for ankle rehabilitation. 