Abstract: Based on the principle that electromagnetic force varies with electromagnetic field,a test device with parallel electromagnetic and mechanical support elements was designed to realize the varying of the system support stiffness with the electromagnetic field strength.By studying and linearizing the mathematical model of this simulation test device,four design rules were given,making sure that the system support stiffness parameter could be randomly controlled by the controllable random electric current.The linearized rule guarantees the linearity of the system support stiffness;the linear random rule engenders the linear relationship between the support stiffness parameter and the controllable random electric current;the rule of significant random stiffness weight brings about obvious randomness of the system support stiffness,and satisfies the demand of testing;finally the rule of the positive system total stiffness ensures the stability of the simulation test device.Consequently,the simulation test device of random stiffness parameter has been constructed according to these four rules.The test results show that the simulation test device can well simulate the random stiffness parameter.