The instrument is realized with three identical composite sensor supporting a feet plate were used to measure the ground reaction force applied by subject during postural balance analysis. A Microsystems based on microcontroller was built in order to drive the instrumentation and a graphical user interface was realized. The signals acquisitions are displayed on the PC screen when the COG moves in the xy plan. After the calculation and programming of the COG coordinates point, the plot of the XG and YG time series of the COG position during a postural balance analysis is easily obtained and recording. The effect of visual input is studied by performing the test with eyes open and then closed. The dynamic parameters show clear indicator of the postural balance. Objective method of diagnosis is to access to postural stability for identifying persons at risk of falling.