In this paper investigates the dynamic stability of Fe3O4 magnetorheological fluid produced by Submerged Arc Nanoparticle Synthesis System which our team has modified, that is, the dynamic stability of magnetic microparticle in Brownian motion. Through this modified system, parameters such as the exact peak current, the time of discharge and off time, and voltage can be preset. The results of the experiment show that the Fe3O4 magnetorheological fluid produced by the modified submerged arc nanoparticle synthesis system has wt 20% and vol 1% surfactants after being mixed with water. After being placed aside for one day and 15 days respectively, the average diameters of the two nanofluid measured with particle size analyzer and TEM are both 40nm. Furthermore, after analyzed through Brookhaven ZetaPlus the zeta potential of the two nanofluid both reach 40mv, which proves that the magnetic nanofluid show superior performance of suspension.