In this paper, a piezoelectric-driven resonant unit for high-viscosity-liquid injection is introduced. For high-viscosity-liquid delivery in low voltage and frequency, a vibrating block is fixed under the rectangular piezoelectric actuator, to transport the vibration to the chamber, leading the unit into resonant state. The valveless chamber is designed eccentrically to promote the tendency of positive flow and diminish the backflow. Numerical simulation and analyses are carried out to optimize the chamber design, and the experiments with liquid in different viscosity, radius of the vibrating block, and the influence of gravity are conducted. The unit achieves a fast delivery speed with a relatively high liquid viscosity compared to the similar study, as the highest flow rate of 52.4, 88.4, and 103.9 ml/min at 100 V, 60 Hz with the liquid of 54.42, 21.13 cP, and water, respectively. The flow rate drops by 40.7%, while the liquid viscosity increases 157.5%.