Magnetic metal belt transmission is a new one in which the initial tension no longer solely, but together with the magnetic attraction force produces the friction force. The influencing factors on transmission ratio are analyzed and numerically simulated in this paper, such as effective haulage force, initial tension, magnetic induction intensity, center distance, diameter of the smaller belt pulley and angle of contact. The change laws of transmission ratio along with these influencing factors are studied. The results show that the transmission ratio of magnetic metal belt transmission increases when magnetic induction density, initial tension and center distance increases, and decrease when angle of contact and diameter of the smaller belt pulley increases. It is pointed out that the angle of contact and diameter of the smaller belt pulley can be reduced accordingly because of the effect of magnetic force, and therefore the transmission ratio can increase by 3〜4 times compared with general belt transmission.