Usually the balance evaluation the center of mass displacement for the analysis of postural control is assessed by means of force platforms. However, most of these devices are stationary, that is the patient is the dynamic element which can generate an evaluation with high subjectivity index. Therefore, this study aimed at developed a reaction force to the ground platform which provides mechanical stimuli controlled to quantify the distribution of the mass center as a function of the angular variation in the elderly ankle in the upright position. The construction of the prototype was divided into 3 steps, based on the two-dimensional movement of the ankle joint. In the 1st stage the construction of the mechanical assembly; in the 2nd stage development of the electronics; and 3rd stage the development of the supervisory system (control system). The force plataform was evaluated following the engineering functional tests such as: characterization and calibration of the sensors, the definition of the transfer function and accuracy of tests of angular movements (+ 10 ° and -10 ° to the movements of inversion and eversion, + 15 and -15º to the movements of dorsiflexion and plantar flexion). For the tests with volunteers were selected 30 volunteers.