This paper presents a fluid powered Motion Socks aimed to prevent deep vein thrombosis (DVT). As the basic design concept, "Safe Area" is introduced, which can assure both safe driving direction for the foot and efficient force transmission. To satisfy this concept, two types of fluid powered actuators with flexible structure are proposed to generate pulling motion and pushing one. The proposed Motion Socks can realize four different motions by using three pull-actuators and one push-actuator. Additionally, in order to measure the posture of the ankle, a sensing device composed of two bending sensors is proposed, which is attached on the inside of Motion Socks. The proposed whole system could successfully promote the blood circulation and its validity was experimentally verified.