For the simulations of elastic constructions actuated by inner pressure we need for the definition of the material model parameters, the data originating from the biaxial test. The paper reviews the biaxial material testing methods, especially the bubble inflation methods. It contains a short summary of the stress analysis of the rotation ellipsoid shells in association with the bubble inflation. The paper shows a developed equibiaxial inflating test using optical measurement method. Two different methods using image processing are showed. The test result of an examined silicone rubber (MED-4930) is presented with it’s material parameters.