MicroCo particles of strong magnetic properties were added into Fe3O4 oilbase magnetic fluids to improve the pressure bearing capability of magnetic fluids rotary seal of corrosion resistant pump.The effects of the volume percent of microCo particles on the sealing water properties of Fe3O4 oilbase magnetic fluids and the temperature rise of the sealing device were investigated.The results show that,with the increase of microCo particles volume concentration in the magnetic fluids,the pressure bearing capability of the magnetic fluids is enhanced for the soft magnetic pole formed on the magnetic tooth surface reduces the gap between the sealing shaft and the magnetic tooth of the sealing structure.With the increase of microCo particles volume concentration in the magnetic fluids,the power dissipation and temperature rise of the sealing device are also increased.The frictional heat between microCo particles,the microCo particle and the sealing shaft during the sealing water contributes to the temperature rise of the sealing device.