Active colloids regarding responsible for charge transfer and electron transfer are in electroless metal bath. Herein, the electrochemical analysis for the catalytic effect of Pd nanoparticles on deposition kinetic and microstructure in the electroless nickel-phosphorous bath was studied. As supported analysis by leaner sweep voltammetry (LSV), the currents for oxidation peaks corresponding to Pd nanoparticles of increasing amount are measured to be enhanced. It shows that Pd nanoparticles have excellent catalytic power for ENpD bath. In addition, the deposition rate analyzed by mixed potential theory (MPT) was found and increased from 0.063 to 0.091 mu g/cm(2)s. However, based on the same nanocatalyst quantity, the deposition rates which actually occurred and are in situely monitored by EQCM are measured to be faster than theoretical value given by MPT. It shows that that the cathodic currents for depositing hydrogen and phosphorous in mixed potential theory could not be neglected when the equilibrium potential reached. As an additional information supported by FE-SEM, the continuous growth of nickel crystal is found after the induction time measured by EQCM. The narrowest distribution of nanosize grain is obtained at 120 s. In addition, the deposited layer of P of higher content is found to exist in the deposited microstructure catalyzed by the Pd nanoparticles of high concentration. (c) 2006 Elsevier Ltd. All rights reserved.