Abstract: Dynamic yield behavior of magnetorheological fluids is investigated by upscaling information of microscale interaction between particles, employing a large-scale molecular dynamical simulation technique, to macroscale bulk behavior. We conduct a stochastic muhiscale model for dynamic yield of magnetorheological fluids based on equivalence of system energy at different scales. It is revealed that the dynamic yield exhibits nonlinear and stochastic fluctuations due to heterogeneity of sequence and number of cluster-sheet reconstructions under shear fields loading, as well as Brownian motion of suspensions with initial random conditions. Meanwhile, we investigate fluctuation of microscale particle motions, relationship between stress and strain, and constitutive relationship of shear rate. It is noted that the microscale thermal fluctuation is far more than macroscalc variations since the upscaling from microscale to macroscale results in degradation of fluctuations. Besides, the macroscale variations relies on external magnetic field as in the constitutive relationship of shear rate, i.e. Bingham model, which is supposed to be considered in the design and optimization of magnetorheological devices.