In order to investigate the copper gap-filling in micro electroplating process with additive(N'N-diethylthiourea),the electrochemical behaviors of electrolyte were analysed by SEM,CVS and XRD,and the electrode dynamic parameters were studied by the Tafei equation.The results show that when N'N-diethylthiourea is used in micro electroplating copper process,an activation polarization is generated to improve the activation energy,the metal ion discharge rate is lowered from 2.221 4 mA/cm² to about 0.076 mA/cm².Therefore,the overpotential is increased,and the crystal nucleus molding speed on the electrode is accelerated;so that the crystal growth speed is decreased from 2.57 μm/min to about 0.17 μm /min,and the leveling ability is increased about 50%.Experiments show that the side effect is lowered effectively,which makes the copper ions get a good filling ability for micro-trenches.Furthermore,some micro trenches in the silicon wafer with the width of 10 μm and aspect ratio of 4:1 are filled by metal copper in micro electroplating process with N'N-diethylthiourea,the electroplating layer have no voids or seams.