Ag thick film conductors were fabricated with Ag powders having different degree of dispersion and glasses having different viscosity, and then the relationship between microstructure and electrical properties of the Ag films was investigated. Under the same processing condition. the Ag thick film that was prepared with the well-dispersed Ag powder and glass having low viscosity had denser microstructure and lower resistance than those of the film which was fabricated with the agglomerated Ag powder and glass having high viscosity It is believed to be due to the fast micro rearrangement kinetics when the well dispersed Ag powder was used, and all the microstructure development kinetics were impeded when low viscosity glass used. It was found that theme fast microstructure development kinetics resulted in the dense microstructure and the lower sheet resistance of the films. Also, the saturation time, at which at a given temperature no further decrease in the sheet resistance was obtained, was found to be shortened when well-dispersed Ag powder and low viscosity glass were used.