An artificial sphincter system having: (1) a hollow object, which has the ability of contraction and expansion; (2) a shape memory alloy (SMA), which is connected with the hollow object, changes its shape to imitate the motion of human muscle by applying different electric current; (3) an electric power to provide different amounts of electric current to the shape memory alloy and let it contract or expand to control the motion of the hollow object to imitate the motion of human muscle; and (4) a photo resistor added between the electric power and the shape memory alloy, which senses the brightness of surrounding light and controls A/D (analog-to-digital) values of the electric power to cause different conditions of contraction and expansion of each part of the shape memory alloy.