The voltage stability is the ability of the power system to provide adequate reactive power under all operating conditions and to maintain stable load voltage magnitude within specified operating limits. The modal analysis method is used to investigate the stability of the power system. Q-V curves are used to confirm the obtained results and to predict the stability margin or distance to voltage collapse based on the reactive power load demand. The modal analysis method is applied to the Western System Coordinating Council (WSCC) 3-Machines 9-Bus power system. The weak buses, which contribute to the critical mode, will be identified by using the participation factors. The Field Programmable Get Array (F.P.G.A) technique is used to solve this problem on–line using the Very High Speed Language (V.H.D.L) technique. Two Spartan 3 cit are used to connect directly between the computer and the network; the first will resave the power information from computer and the second will transmit the power information to the network.