To maintain Power Integrity in a high speed system, an effective methodology for suppressing the cavity-mode resonances peaks is presented. The optimal values and the optimal positions of the decoupling capacitors are found using Particle Swarm Optimization, which leads to optimum impedence of power plane loaded with decoupling capacitors. A pseudo-code, to find the optimum number of capacitors and their values, is presented, by which impedance of loaded board is matched below the target impedance of the system.