Abstract: To research the influence of the ink viscosity on the ink flow characteristics in microscale during the printing process, the ink viscosity on the ink flow characteristics was first analyzed in theory. Then, the effect of the viscosity on the ink flow characteristics was simulated in conditions of slip and no slip using FLUENT that is professional fluid simulation software. Results show that under two conditions, the maximum pressure increases with the increase of the viscosity. Under no slip condition, the viscosity has no effect on the ink velocity. However, under the slip condition, with the increase of the viscosity, the ink velocity increases first and then decreases, however, remains unchanged fianlly. By contrast, considering the slip or not, it has great influence on the maximum velocity of ink. Therefore, it is necessary to consider the slip when analyzing the influence of the viscosity on the ink flow characteristics.