Abstract: A new type electricrheological (ER) smart isolator is developed with ER smart damper and rubber isolator. The new type ER smart isolator is firstly designed. Controlled force formulas of rotation ER damper are proposed. The functions between electric field intensity and shear transform of ER damper are presented. Two kinds of hysteretic models are proposed as pseudo-displacement limited model and pseudo-friction model. Based on the controlled characteristic of ER smart isolator, friction control rule and formulas are then put forward and coded into a program for application. Finally, a SDOF structure with ER smart isolator is analysed. The results show that: two kinds of ER isolators are both efficiency for displacement decrease in the isolation layer, and the acceleration does not increase at the same time.