Aimed at the purpose of sophisticated instruments six degree-of-freedom （6-DOF）semi-active vibration isolation, a 6-DOF vibration isolation platform based on six novel doublepiston magnetorheological fluid dampers is proposed. Firstly, one prototype damper was designed and fabricated. The dampers dynamical properties curves were obtained by a series of experiments, and hyperbolic tangent model was established. Secondly, a 6-DOF semi-active vibration isolation platform using of those novel dampers based on the Stewart platform structure was designed. The results from the simulation study on vibration control performance of platform showed that the platform had efficient vibration isolation effect in all six directions. The proposed 6-DOF platform has advantages of light mass of its own and compact structure with obvious vibration isolation effect, which satisfies the needs in 6-DOF semi-active vibration isolation of precision instruments and equipments.