Abstarct: In many applications which required linear motion, using linear motors is prefered to rotary motors. Among the variety of linear motors, permanent magnet motors are highly considered due to low-loss, small electrical time constant and fast response. However one of the disadvantages of linear permanent magnet machines is cogging force that causes ripple in the thrust force as well as movement disorders. Linear machines are built in two types includ single-sided and double-side. In double- sided linear motors, normal force comes smoother to moving part. Generally, this type outperforms simillar motor with the same structure.The aim of this study is to optimum design of double- sided permanent magnet linear synchronous motor to reduce the force ripple. So, at first different methods reducing the force ripple including change of slot aperture width, magnets dimensions and chamfer the tip of the tooth force ripple are studied. Then ripple sensitivity parameters change in each method is determined. A permanent magnet linear motor with nominal specifications is considered and these cases are examind by using finite element model of machine. Finally, an optimal hybrid method is presented to effectively reduce the force ripple.