The invention relates to an adjustable-rigidity support device based on a dielectric elastomer. The adjustable-rigidity support device comprises a base, an elastic cantilever beam and a dielectric elastomer rope belt, and the elastic cantilever beam and the dielectric elastomer rope belt are connected with the base; and the elastic cantilever beam is connected with the dielectric elastomer rope belt, the other end of the elastic cantilever beam and the other end of the dielectric elastomer rope belt are connected with the base, a detection instrument is arranged on the elastic cantilever beam,and the dielectric elastomer rope belt is composed of an elastomer film and a flexible electrode. The adjustable-rigidity support device based on the dielectric elastomer is simple in structure, quick in response, convenient to control, low in power dissipation and capable of applying voltage to the dielectric elastomer rope belt to control the rigidity and damping of the structure, and thereforevibration control within a wider working band is achieved.