Abstract: Combining the micro structure and the interaction between two particles in an electrorheological fluid thaTis calculated by the modified dipolemodel and the conductivity model respecTively, the shear stress-strain relationships of the electrorheological fluid were set up. On this basis, and considering the fracture and reconfiguration process in the post-yield state of this material, its dynamic yield stress was obtained. The calculation indicates that the dynamic yieldst ress low er than staTic yield st ress by abou t 25%. In addiTion, the dynam ic yield st ress of theelect ro rheo logical f lu id increases nearly linearly w ith the vo lume f racTion at the small vo lumef racTion and get s their max imum s at rather large vo lume f racTion s, 0. 4～ 0. 5.